# Harvard Intermittent Fasting Researcher Reveals the Clinical Truth Behind Fasting and Real Results

https://www.youtube.com/watch?v=dJ4EdhtGDQk
Translation: es

[00:00] The impact of intermittent fasting on

[00:01] aging is hugely exciting. If you look at

[00:03] autophagy as a function of the number of

[00:05] hours someone's been fasting, you tend

[00:07] to see an increase in humans around 11

[00:09] to [music] 13 hours and and it goes up.

[00:11] And they have consistently reported that

[00:13] intermittent fasting seems [music] to

[00:14] lower blood pressure and the effect's

[00:16] about equivalent to taking a single

[00:18] antihypertensive medication.

[00:20] >> We found interestingly that intermittent

[00:22] fasting makes your hunger levels more

[00:24] even keeled [music] throughout the day.

[00:26] >> In these studies, they'd have people

[00:27] typically about 50% of their daily

[00:29] calories for breakfast and they lost

[00:31] significantly more weight. And not only

[00:33] did they lose more weight, but [music]

[00:35] they were less hungry, which I find

[00:36] amazing, right?

[00:37] >> eating more earlier in the day, they

[00:40] lost more weight, and they felt less

[00:41] hungry.

[00:42] >> Correct. What do you think is the

[00:43] fastest way towards elevating your blood

[00:45] sugar levels? Big Mac, being sedentary,

[00:48] or losing sleep? And the answer is

[00:49] losing sleep.

[00:54] >> We've always been taught to think about

[00:56] nutrition in terms of what we eat,

[00:58] calories, fats, proteins, carbs, and so

[01:01] on. But what if one of the most powerful

[01:03] levers that we have for human health has

[01:05] nothing to do with what you eat at all

[01:07] and everything to do with when you eat

[01:09] it. Because every day our bodies are

[01:12] operating on this internal clock, a

[01:13] circadian rhythm that governs everything

[01:15] from your metabolism to your hormones to

[01:18] how your cells repair themselves. And

[01:19] when what we eat is out of sync with

[01:21] that rhythm, we may be working against

[01:23] our own biology. Today's guest is one of

[01:25] the world's leading scientists studying

[01:27] exactly that. Dr. Courtney Peterson is a

[01:30] leading researcher in nutrition science

[01:31] and circadian metabolism, currently

[01:33] based out of Harvard University. Her lab

[01:35] has conducted some of the first

[01:37] randomized control trials in humans on

[01:40] intermittent fasting, helping us to

[01:42] redefine how we think about fasting, not

[01:44] as a tool for restriction, but as a way

[01:46] to realign the body with its natural

[01:49] biological rhythms. And what's

[01:50] fascinating about this, um, is that the

[01:52] benefits we see, from weight loss to

[01:54] blood sugar control to blood pressure,

[01:57] they don't seem to come from these magic

[01:59] metabolic boosts, but from something

[02:00] much simpler. Changing when we eat

[02:02] changes how our biology responds. This

[02:05] is about separating signal from noise,

[02:08] what data actually shows, what we still

[02:10] don't know, and how to apply this in a

[02:12] way that fits real life. Because the

[02:14] most powerful interventions are often,

[02:16] as we know, the ones that are both

[02:18] effective and sustainable. Welcome to

[02:20] the Lemon Room.

[02:21] Hi Courtney.

[02:22] >> Hey Chris, how are you?

[02:23] >> Welcome Welcome to my living room.

[02:24] >> Thank you.

[02:25] >> So, I thought we would start with um

[02:28] some definitions, cuz I think everyone

[02:30] has heard of this term intermittent

[02:32] fasting through one um resource or

[02:35] another. And I think we often associate

[02:36] that with fat loss mainly, um or some

[02:39] kind of dietary control.

[02:40] Given your subject matter expertise, why

[02:44] don't we start with your definition of

[02:45] what that means?

[02:47] >> Sure. Um so, intermittent fasting is

[02:50] sort of a broad category of approaches

[02:51] that alternate periods of eating and

[02:53] extended fasting.

[02:55] And I was recently part of like an

[02:57] international consensus committee of

[02:59] scientists and experts around the world.

[03:01] There were about 37 of us. And we

[03:03] convened and there's a little bit of

[03:04] debate, but what we are now defining

[03:06] intermittent fasting as is fasting for

[03:08] at least up to 48 hours at a time and

[03:11] doing that on a periodic basis.

[03:14] So, there

[03:15] a lot of different types of intermittent

[03:16] fasting and I like to because they're so

[03:18] different, I like to group them into

[03:19] three broad categories. So, this first

[03:22] sort of category, I kind of think of it

[03:24] as like periodic water only fasting,

[03:26] where you pick some number of days per

[03:28] week or per month to have a 24-hour or

[03:31] longer water only fast. So, an example

[03:33] of this is in a lot of religious

[03:35] traditions, they'll often fast one day a

[03:37] week uh every week. Another example

[03:39] would be something called alternate-day

[03:41] fasting, where every other day you have

[03:42] a complete water only fast. Uh that's

[03:45] far more extreme, so I don't recommend

[03:47] it for most people, but nonetheless

[03:49] there are are studies on that in humans.

[03:51] Uh the second type of

[03:53] and this is where it's a little bit more

[03:54] debated whether these are genuinely

[03:56] intermittent fasting or not or what are

[03:58] called um

[03:59] either intermittent energy restriction

[04:01] or modified fasting. In these

[04:03] approaches, you eat a very low-calorie

[04:05] diet some number of times per week or

[04:08] per month. So, by very low-calorie diet,

[04:10] we usually mean about 800 calories a

[04:12] day. I like to translate that into being

[04:14] like one meal a day. So, examples of

[04:17] this would be the 5:2 diet, which is

[04:18] very popular in Europe.

[04:20] Well, you pick like 2 days a week,

[04:22] either consecutive or non-consecutive to

[04:24] eat about the equivalent of one meal a

[04:26] day.

[04:27] And then

[04:27] >> normal eating for the rest of the five

[04:29] days.

[04:30] >> eating, yep. Yep, so however much you

[04:32] feel like eating. So, and you may

[04:34] slightly overeat on the other days, but

[04:36] it's not enough to compensate. You still

[04:38] tend to lose weight. Another example of

[04:40] this, Valter Longo has created something

[04:42] called the fasting mimicking diet.

[04:45] And that's where you pick like 5 days in

[04:46] a row to eat a very low-calorie diet.

[04:48] And And the

[04:50] the sort of goal with that is to

[04:52] mimic a lot of the benefits of

[04:54] longer-term fasting, but without having

[04:56] to have that 24-hour water-only fast,

[04:58] exactly. And then the your sort of third

[05:00] broad And there's some debate like

[05:02] whether are you extending your fast? Are

[05:03] you not? How much are you really getting

[05:06] those benefits of benefits of water-only

[05:08] fasting? And then your third category of

[05:11] approaches are your daily intermittent

[05:12] fasting approaches, which is just what

[05:14] most people think of when you say

[05:15] intermittent fasting. And we have a term

[05:18] for them called time-restricted eating,

[05:19] not not the best name. Um but these are

[05:22] approaches where you have a 14-hour or

[05:24] longer daily fast. So, what that means

[05:27] is you're eating within a a consistent

[05:29] 10-hour window each day. And by

[05:31] consistent, I mean it's not like, you

[05:33] know, one day you start eating at 8:00

[05:34] a.m. and the next day you start eating

[05:36] at noon. You pick like a consistent

[05:38] time. And part of the goal of that is to

[05:40] um kind of get your body to adapt to

[05:42] that time and and kind of um

[05:44] sort of optimize something we'd call

[05:45] like your circadian biology, but we can

[05:47] go into that later. But these are sort

[05:49] of your broad categories of approaches.

[05:52] Among these types of approaches, the

[05:53] most popular is known as the 16:8 diet.

[05:56] And so this is eating in an 8-hour

[05:57] window um and having 16 hours of fasting

[06:00] every day.

[06:02] >> That seems like the least

[06:04] self-punishment.

[06:05] >> It It is. And in fact, I mean, when I

[06:08] first got into the field, like so it was

[06:10] 2010

[06:12] and I remember hearing a podcast

[06:15] where they said um they talked about

[06:17] this crazy study or it was, you know,

[06:19] equivalent of podcast back then where

[06:20] they had people eat in a 4-hour period

[06:23] and fast 20 hours a day and they said,

[06:25] "Oh, this will improve their health

[06:26] dramatically." Which turned out not to

[06:27] be the case in the study, but I thought

[06:29] that's so interesting like

[06:31] um how do we get some of those benefits,

[06:34] but do something that's a little bit

[06:35] less extreme?

[06:36] And so I think with this daily

[06:38] intermittent fasting, you have the

[06:40] ability to do something that's kind of

[06:42] sustainable, but sort of get those

[06:43] long-term benefits. Whereas some of

[06:44] these other approaches where you have

[06:47] water only fast for some number of days

[06:48] per week, I think they're much more for

[06:51] people who are more motivated and want

[06:52] to go to the extreme, but I think for

[06:53] most people we need something we can do

[06:55] something like 5 days a week and still

[06:57] get some of those benefits.

[06:58] >> guess some people kind of like ripping

[06:59] off the band-aid though and just get it

[07:02] done in one day if if there is the

[07:04] equivalent upside.

[07:06] >> There Yeah, there is.

[07:08] >> Not me, by the way.

[07:09] >> No, no. I I think also, I mean,

[07:12] when you do the daily intermittent

[07:14] fasting, we the data generally suggests

[07:17] there's no negative impact on your

[07:18] muscle mass, which is great.

[07:21] There is some data from the UK that

[07:23] suggests if you fast for more than 36 to

[07:26] 48 hours at a time, you will lose extra

[07:28] muscle mass. Yeah. So there I think

[07:30] there's like a sweet spot, a dose that's

[07:32] like doable in real life, but not going

[07:34] to have some of the negative effects.

[07:35] Now, that might be helpful, you know,

[07:37] these more extreme fast might be helpful

[07:38] with someone who might have severe

[07:40] obesity or something else or they have

[07:42] hypertension and they're trying to get

[07:43] to a goal quickly.

[07:45] But I like some of these more

[07:46] sustainable daily things that you

[07:48] >> How did you end up studying this? And I

[07:50] think

[07:51] probably more importantly, like what is

[07:53] it that you're actually studying within

[07:55] those broad definitions?

[07:57] >> Yeah, I kind of got interested in the

[07:58] concept of, you know, therapeutic

[08:01] fasting or fasting to improve people's

[08:03] health and in the sort of um

[08:06] my backstory is I used to uh I used to

[08:09] be in physics. So I studied the physics

[08:11] of the early universe. I studied

[08:12] something called called cosmology.

[08:14] >> Yeah.

[08:15] >> So I was studying the early universe

[08:17] less than a second after the Big Bang

[08:18] and we're coming up with all these crazy

[08:20] theories and like what particles

[08:21] existed.

[08:22] >> isn't there?

[08:22] >> Uh inflation is what I was studying. So

[08:25] um and we think inflation's important

[08:26] cuz it gave rise to galaxies and

[08:29] structure throughout the universe.

[08:31] Um but I realized like 99% of the

[08:34] theories we were working on were going

[08:36] to be wrong.

[08:37] >> Mhm.

[08:37] >> And I just I, you know, it was the time

[08:40] that Steve Jobs was going around and

[08:41] giving talks,

[08:43] uh graduation speeches, and he was

[08:45] talking about if he had too many days in

[08:46] a row where he felt um that if he

[08:50] continued if he died tomorrow and he was

[08:52] doing what he was doing today and he was

[08:54] not happy with that, then he knew he

[08:55] needed to pivot course course. And for

[08:58] me I was like, I'm not quite as extreme

[08:59] as Steve Jobs, but my version of that is

[09:01] if I fast forward I'm 65, I'm looking

[09:04] back on my career.

[09:07] If I took a risk and failed, would I be

[09:09] happy taking that risk?

[09:12] And in physics I would only be happy if

[09:13] I succeeded,

[09:15] but not if I failed.

[09:17] Um and so then I just thought I want to

[09:19] be in a space in which if I failed I was

[09:21] glad I was there and took the risk. And

[09:23] so so So part of that's another way of

[09:25] saying like the problem is so important

[09:27] that you know you're working on

[09:28] something of value to humanity that it

[09:30] even if you failed like it was the right

[09:31] problem to work on.

[09:33] And for me I'd always been interested in

[09:35] health and nutrition. I was sporty as a

[09:37] kid. I mean, I played soccer. I broken

[09:39] my nose twice playing soccer. So, you

[09:41] know, pretty competitive in in that

[09:42] regard, but also like a science nerd,

[09:44] you know, two two two kind of

[09:46] personality types in the same person.

[09:48] And um had always been interested in

[09:50] health and realized that a diet a poor

[09:53] diet is actually the leading cause of

[09:54] death worldwide. So, it's roughly about

[09:57] a third of all attributable deaths

[09:59] worldwide are due to poor diet, followed

[10:00] in second place very closely by

[10:02] infectious diseases.

[10:04] And we dramatically underfund nutrition

[10:06] research, and there's not enough work.

[10:08] And so, I got very passionate about food

[10:09] as medicine and just trying to improve,

[10:12] you know, trying you know, hoping that

[10:13] that could be my contribution to

[10:15] society. I'm interested in both diet

[10:18] quality and fasting, but I think fasting

[10:20] is something that

[10:23] you know, is almost accessible to

[10:24] everyone.

[10:24] >> Mhm.

[10:25] >> Regardless of your income level,

[10:26] regardless of what you do. I think

[10:28] there's something in meal timing for

[10:30] everyone. And so, I got very passionate

[10:32] about that and and trying to do like

[10:34] more sophisticated research where we can

[10:36] really understand how it affects the

[10:38] human body.

[10:39] >> That's what I love so much about this

[10:40] particular topic is it's very

[10:42] accessible.

[10:43] >> Yes.

[10:44] >> And and especially given how exciting

[10:45] the data looks, something that we can

[10:48] all engage with in our own way.

[10:50] >> Yes.

[10:51] >> So, so let's talk about the data and and

[10:53] what you found and and

[10:55] you know, what your research is

[10:56] suggesting.

[10:57] >> Yeah. So, one of the biggest questions I

[10:59] get is it good for losing weight or not?

[11:01] Because I think that's the big

[11:02] motivation. And so, back a decade ago

[11:04] when some of the first studies came out,

[11:06] it's they suggested that uh these mice

[11:09] or these rodents lost a lot of weight.

[11:11] Um interestingly, in rodents, it

[11:15] suggested that in the data suggested

[11:17] that intermittent fasting was helping

[11:18] them lose weight by burning extra

[11:20] calories.

[11:20] >> Mhm.

[11:21] >> And so, this is many years ago, but my

[11:23] lab was one of the first to study this

[11:25] daily intermittent fasting in humans.

[11:27] Um we did one of the first what are

[11:29] called randomized control trials. So,

[11:30] these are just studies that are very,

[11:32] you know, rigorous and are done to the

[11:34] right right standard. Um and

[11:37] uh what we and others showed at the time

[11:39] is that this daily intermittent fasting,

[11:41] at least if you're eating in an 8-hour

[11:43] period or less, does help you lose

[11:46] weight.

[11:47] Um and we also did a a bunch of really

[11:49] cool tests where we brought people into

[11:51] the lab and we measured how many

[11:52] calories they burn. Cuz we were

[11:54] interested at the time. We didn't know,

[11:55] okay, does back then, I mean, there were

[11:56] only maybe like 20 studies on

[11:58] intermittent fasting in humans. We

[11:59] didn't know whether the reason it helps

[12:03] you lose weight is because it suppresses

[12:05] your appetite or it helps you burn more

[12:06] calories. Um so, we brought people into

[12:09] the lab and we had them stay overnight

[12:11] in what looks kind of like a little bit

[12:12] of a fancy not so that fancy, but like a

[12:15] a fancy dorm room.

[12:16] >> Yeah.

[12:16] >> Um and these devices are called

[12:19] respiratory metabolic chambers, but we

[12:21] can measure how much oxygen people

[12:23] breathe in and how much carbon dioxide

[12:25] they breathe out. And from this

[12:27] information, we can calculate how many

[12:30] calories they're burning and then how

[12:31] much of that is fat.

[12:32] And the really interesting thing we

[12:34] found is that intermittent fasting does

[12:35] not help you burn more calories. So, you

[12:36] know, myth myth busting there. Uh it

[12:39] doesn't look like you magically burn

[12:41] more calories. One of the other things

[12:43] we looked at was people's appetite. And

[12:45] we looked at that both in terms of

[12:47] hormones that control appetite, but also

[12:50] like what do they report? Cuz sometimes,

[12:52] you know,

[12:53] your hormones may change, you may not be

[12:55] as hungry. So, there's not always like a

[12:57] perfect relationship there. Um but we

[13:00] found interestingly that intermittent

[13:02] fasting makes your hunger levels more

[13:04] even-keeled throughout the day, which is

[13:07] the exact opposite what I of what I

[13:08] thought would have thought. I would have

[13:09] thought that with the intermittent

[13:11] fasting, there periods where you're like

[13:12] super like I don't want to eat anymore,

[13:14] and then other times where you're just

[13:16] like, I'm so hungry. I just need to eat

[13:18] something.

[13:18] >> of these chambers I see you and and

[13:21] >> Yeah.

[13:21] >> and I don't know if this was

[13:22] psychological, I'm certain it was, I

[13:24] immediately felt hungry.

[13:26] >> It

[13:27] might have been.

[13:27] >> There's like, now I need to eat

[13:28] something. Yeah.

[13:29] >> There's studies suggesting that if you

[13:30] hint to people that they might be

[13:32] hungry, they

[13:32] >> Yeah, I was very susceptible to that.

[13:34] How long were they in there for? I'm

[13:36] assuming 24 hours.

[13:37] >> Yeah, 24 hours. So, they were in there.

[13:38] So, um but we did find a decrease in a

[13:42] hunger hormone called ghrelin in the

[13:44] morning. And then we also measured one

[13:46] of the satiety hormones. Um it's called

[13:48] PYY.

[13:49] And we found that in the middle of the

[13:52] evening that satiety hormone was

[13:54] actually higher.

[13:55] So, at certain kind of points of the

[13:56] day, people's hunger levels seem to be

[13:58] actually lower.

[14:00] >> Yeah.

[14:00] >> And interestingly, you know, now sort of

[14:03] collecting the data from my lab and

[14:05] other people's lab, what we now know is

[14:07] throughout most of the day intermittent

[14:08] fasting makes you less hungry.

[14:10] There seems to be for some types of

[14:12] intermittent fasting, there seems to be

[14:13] a window about 1 to 2 hours between

[14:15] before bedtime where they're more hungry

[14:17] than if they didn't do intermittent

[14:19] fasting. So, if you can kind of make it

[14:21] over that hurdle at the end, um then I

[14:24] think you're in a good position.

[14:25] >> Wait, let me let me just clarify.

[14:27] >> absolutely.

[14:28] >> So, the people that did intermittently

[14:30] fast were less hungry for the last 2

[14:33] hours of the day than the people who

[14:35] didn't.

[14:36] >> Uh the opposite. So, people So, for most

[14:40] of the day, the people who did did

[14:41] intermittent fasting were less hungry.

[14:43] But 1 to 2 hours before bedtime, they

[14:45] were more hungry.

[14:46] >> Huh.

[14:46] >> So, they if they can make it over that

[14:48] hurdle before bedtime, we find they're

[14:51] better cuz they get a they get a

[14:52] competitive advantage over most of the

[14:53] day.

[14:54] >> Sure.

[14:54] >> Just that like little zone before

[14:57] >> And is you know, I think one of the big

[14:58] pushbacks,

[15:00] certainly that I've seen, is you know,

[15:03] you're you're

[15:04] consuming less calories because you've

[15:06] got a narrower window to window to eat.

[15:08] >> Correct.

[15:09] >> What is there above and beyond the

[15:11] energy deficit that you're creating that

[15:13] indicates that this is a valuable tool?

[15:15] >> Yeah. Uh um sure. I'm going to finish

[15:17] this question and then I'll answer your

[15:19] question. Absolutely. Absolutely. So,

[15:21] now we have a pretty sense of how much

[15:24] um at least time restricted eating helps

[15:26] you cut calories. These different types

[15:28] of intermittent fasting, they help you

[15:29] cut calories to a different degree and

[15:31] and some of them are more sustainable in

[15:33] the long term. Like there's some types

[15:34] and I won't probably don't have time to

[15:35] go through it today that you know, just

[15:37] the sustainability isn't there at a year

[15:39] at a year long. But we do see pretty

[15:41] good sustainability with the time

[15:43] restricted eating.

[15:44] Um we our best data now suggests that it

[15:47] helps you cut calories by about if you

[15:49] have obesity by about 250 calories a

[15:52] day.

[15:53] Um which is pretty good.

[15:54] >> Yeah.

[15:54] >> That's about an extra 2 lb a month.

[15:57] Which may not sound like that big given

[15:58] that we're in the era of GLP-1s or GLP-1

[16:01] receptor agonists.

[16:03] But to put it in context, we have a lot

[16:04] of debates in nutrition science about

[16:07] low-carb versus high-carb diets

[16:09] and the differences are much smaller.

[16:11] >> Sure.

[16:11] >> So if someone's going to focus, I'd

[16:14] rather have someone focus on when to eat

[16:16] than how much of certain macronutrients

[16:18] to get at least for losing weight. There

[16:19] are other reasons why I think we do need

[16:21] to think about diet quality and I

[16:22] actually think diet quality is super

[16:23] important.

[16:24] >> Mhm.

[16:25] >> Um but it seems to be less important

[16:26] than avoiding processed foods.

[16:28] So Kevin

[16:29] >> For for weight loss specifically.

[16:30] >> Correct. Correct. Yes. So Kevin Hall did

[16:31] this amazing study at the NIH showing

[16:34] that when you put people on an

[16:35] ultra-processed food diet they overeat

[16:38] by roughly 500 calories a day. So it's

[16:40] massive. So this is a moderate to medium

[16:42] effect. But you know, it still gives you

[16:44] a competitive advantage. Now if you're

[16:46] already lean and healthy, you may not

[16:48] see as big of effects as I'm as I'm

[16:50] stating. But in the long run we see pip-

[16:52] people typically lose about 4 to 7% of

[16:55] their body weight.

[16:56] >> Mhm.

[16:57] >> And for reference, so I'm an obesity

[16:59] researcher. Um our gold standard for

[17:01] weight loss, our goal is at least 5%

[17:03] weight loss for people. So this puts you

[17:04] in that range, right? The GLP-1s, you

[17:07] can lose a lot more.

[17:09] So some data suggests in the real world

[17:11] that with the GLP-1s that um

[17:14] in the real world people lose about a

[17:16] third as much weight as they do in the

[17:17] clinical trials, and then there's also

[17:19] some data suggesting that people tend to

[17:21] regain that weight

[17:22] >> Yeah.

[17:23] >> uh within 2 years, and when they regain

[17:24] it, they regain more body fat,

[17:27] unfortunately. So,

[17:28] >> That That I think is a whole separate

[17:30] episode, but I'm my concern I'm

[17:31] concerned about the the

[17:33] >> Now, we don't Now, in fairness, we don't

[17:35] have data

[17:36] >> Yeah.

[17:36] >> on intermittent fasting up to 2 years.

[17:38] So, you know, I'm I'm insinuating well,

[17:40] it could be still helpful for folks, but

[17:42] we don't know. These are questions we we

[17:43] need to figure out.

[17:44] >> certainly makes sense for long-term

[17:46] sustainable fat loss that you do that

[17:48] less rapidly. Right? Like

[17:51] >> so. I think the reason My guess is the

[17:53] reason that we see excess

[17:56] We see people losing too much muscle

[17:58] mass with the GLP-1s is just how rapidly

[18:00] they're losing weight. I don't think

[18:01] there's anything special about GLP-1s.

[18:03] My guess is the deficit is just too

[18:04] much.

[18:05] >> Yeah.

[18:06] >> Um all a guess. Um but I will tell you,

[18:09] I mean, we did a review of all the

[18:10] literature a couple years ago. About 75%

[18:13] of all studies looking at

[18:15] time-restricted eating as long as the

[18:18] eating window was 8 hours or less

[18:19] reported weight loss benefit. So, we

[18:21] have really good data if you look at

[18:24] what are called meta-analyses that it

[18:25] helps you lose weight.

[18:27] Um one of the other questions are like,

[18:28] "Well, is this any better or worse than

[18:30] calorie counting?"

[18:31] >> Sure.

[18:32] >> And the data suggests it's about equal.

[18:34] But people tend to like it better.

[18:35] >> Yeah.

[18:36] >> People tend to not like calorie

[18:36] counting, which is hard, you know, cuz

[18:38] you have to know roughly the calorie

[18:40] content of a lot of food. It takes a lot

[18:42] of work. So,

[18:42] >> Well, it certainly feels like less

[18:44] friction.

[18:44] >> Correct.

[18:45] >> say just eat within this window.

[18:46] >> Correct. Exactly.

[18:47] >> that note, does

[18:48] have you Have we controlled for

[18:51] the type of food that people are eating

[18:53] within that window? And And by that, I

[18:54] mean,

[18:55] >> Yes.

[18:55] >> when when calories are controlled, so

[18:57] you say that window the calorie

[18:59] consumption was 2,000.

[19:01] >> Mhm.

[19:02] >> Have we controlled for if it was 2,000

[19:04] calories from processed food or

[19:06] unprocessed food? I assume the weight

[19:09] loss is still very similar, probably not

[19:10] as good with processed food, and

[19:12] certainly not as good for your health.

[19:14] >> Yeah.

[19:14] >> But but that would explain why

[19:17] it feels a bit more easy to adhere to.

[19:20] >> Yes. No one has. There are small number

[19:22] of studies testing intermittent fasting

[19:25] in combination with like a Mediterranean

[19:27] diet or a low-carb diet.

[19:29] And some of those studies report

[19:31] extra benefits.

[19:33] Um but we they're not we don't have many

[19:35] of those studies yet, so I'm not ready

[19:37] to say we have great data for that. Um

[19:39] and then going back to and then let me

[19:41] also add 10-hour windows, which a lot of

[19:44] people are excited about. We don't have

[19:45] good enough data to suggest um they help

[19:48] you lose weight. The effects seems to be

[19:51] less. I don't think that means there's

[19:53] no effect there. I think the effect's

[19:55] just a lot weaker with eating in a

[19:57] 10-hour window. I think

[19:58] >> Well, but I'm asking for a friend here.

[19:59] What's the what's the maximum amount of

[20:01] time

[20:02] one can get away with

[20:04] eating for in that in that window? So,

[20:08] how can we increase pleasure the most by

[20:10] making the window as big as possible,

[20:11] but still get the benefits?

[20:13] >> Yeah, I think it

[20:15] it depends. I mean, my my sort of

[20:17] attitude towards these things is pick

[20:19] something you can do 5 days a week, five

[20:21] out of 7 days a week and stick with it.

[20:23] There is a nice study in rodents, as

[20:26] well as we have work in our lab, where

[20:28] we've done analysis saying, "Okay, what

[20:30] if people only stick with it 5 days a

[20:31] week? Do they still get benefits?" And

[20:33] yes, they absolutely do.

[20:35] Um

[20:36] the benefits are a little bit less,

[20:37] obviously, than 7 days a week, but I

[20:39] think we can now say that if you follow

[20:42] it 5 days a week, it's worth your time.

[20:45] So, I would say pick what you can do 5

[20:48] days a week most weeks and stick with

[20:50] that. Um you're going to get my guess is

[20:52] you're still going to get benefits with

[20:54] 10-hour window, but I just don't want

[20:55] people to think they're going to get as

[20:58] big of a benefit as we see with 8-hour

[20:59] windows. And most of our data on humans

[21:01] is on 8-hour windows.

[21:02] >> we know if that benefit increases even

[21:04] more if that window is shorter?

[21:06] >> Uh we don't know yet. People have tested

[21:09] shorter windows. Um there's like one

[21:12] study I know maybe there are two studies

[21:14] that have tested smaller windows. One

[21:16] found no benefit, the other found a

[21:18] benefit. So I don't know. We don't have

[21:19] quite enough data yet.

[21:21] >> really fascinating because I think when

[21:23] we

[21:24] you know

[21:24] switch on any kind of media outlet and

[21:26] we see a story about intermittent

[21:27] fasting, we're told so many different

[21:29] things.

[21:30] >> [laughter]

[21:30] >> You know, eat one meal a day, have a

[21:31] 10-hour window, like it's And the

[21:33] reality is we don't know for sure.

[21:35] >> We don't know. That's right. And we

[21:36] don't even know how many meal meals you

[21:38] should eat. Now we have some data from

[21:40] our lab where we think you might get

[21:42] some extra benefit and I'm happy this

[21:44] allows me to pivot to another topic, but

[21:46] um

[21:47] that suggests maybe skipping meals you

[21:49] may not get as much benefit with

[21:51] intermittent fasting at least for blood

[21:53] sugar control.

[21:54] So in one of our studies where we looked

[21:56] at time-restricted eating, we put CGMs

[21:58] on participants. So CGMs are little

[22:00] blood sugar monitors. You can measure

[22:02] your blood sugar levels across the day.

[22:05] And we had people eat three meals a day

[22:09] within a 6-hour window. So it's pretty

[22:11] you know, it's a little bit more on the

[22:12] extreme end. versus eating those same

[22:14] three meals a day over a 12-hour window.

[22:17] So then we looked at their blood sugar

[22:18] levels over the course of the day. And

[22:20] the fascinating thing we found is um

[22:23] when people did time-restricted eating,

[22:26] we didn't really see a big difference in

[22:28] the blood sugar response at breakfast,

[22:30] but we saw huge effects at lunch and

[22:32] dinner and especially lunch. And what I

[22:34] mean by that is when participants or

[22:38] when people in the study

[22:40] did TRE their blood sugar levels at

[22:43] lunch didn't spike very high at all. It

[22:45] was like it was like they were

[22:46] completely blunted. They just didn't go

[22:48] up very much.

[22:49] And I think what's happening is if you

[22:51] eat a bunch so you know, rule of thumb

[22:54] takes about 4 to 6 hours to digest a

[22:56] meal. So that's that's how long it

[22:58] typically takes blood sugar levels to go

[22:59] back to normal.

[23:01] So I think what's happening is if you

[23:02] eat a meal at breakfast and your you you

[23:04] know, your blood sugar levels will go

[23:06] up, but your blood sugar hormone insulin

[23:08] will go up, too.

[23:09] >> Yeah.

[23:10] >> And if you eat another meal before your

[23:12] blood sugar levels and your insulin

[23:13] levels have gone back to where they were

[23:16] before the meal, you already have that

[23:18] extra insulin around. And so, when you

[23:19] eat your next meal, that other insulin's

[23:21] already there, so it's ready to do its

[23:22] job. So, we think actually you will get

[23:25] some perhaps more benefits

[23:27] from not necessarily skipping meals.

[23:29] Now, we don't have clear evidence on

[23:31] this. This is, you know, just

[23:33] speculation based on data we have. Um

[23:36] but yeah, so but we don't The punchline

[23:38] is we don't know for certain. We have no

[23:39] idea how many meals a day. Um

[23:42] outside of weight loss, I think the

[23:45] other interesting areas for me, I think

[23:47] we have really good data now that this

[23:49] daily intermittent fasting lowers blood

[23:51] sugar levels, at least in people who

[23:53] have blood sugar problems.

[23:55] And the other area where I think we have

[23:57] really good data is on blood pressure.

[23:58] >> Mhm.

[23:59] >> Um

[24:00] and so, um

[24:02] in people with blood sugar, uh I just

[24:05] wrote an article where we reviewed all

[24:07] the intermittent fasting studies in

[24:08] patients with type 2 diabetes, type 1

[24:11] diabetes, gestational diabetes, and

[24:13] pre-diabetes.

[24:14] And the amazing thing, so there were 28

[24:16] studies we found on intermittent fasting

[24:18] in patients with type 2 diabetes.

[24:20] And 27 out of 28 of them reported a

[24:22] benefit.

[24:23] >> No way.

[24:24] >> So, and we're seeing quite good benefits

[24:26] in patients with type 2 diabetes. So, I

[24:28] was actually quite impressed with the

[24:30] level of consensus cuz I mean, these are

[24:32] This is across the 5:2 diet, you know,

[24:35] fasting mimicking diet.

[24:37] >> types of

[24:38] >> intermittent fasting. Yeah. That have

[24:40] been tested in patients in people who

[24:42] have type 2 diabetes. So, I think, you

[24:44] know, um now in people who are healthy,

[24:48] studies are mixed. Sometimes they

[24:49] suggest a blood sugar benefit, sometimes

[24:51] they don't. But in patients who have who

[24:53] have who have blood sugar problems,

[24:54] there's a benefit. I think what that

[24:56] means is there's probably also a benefit

[24:57] in healthy people, it's just small. It's

[24:58] hard to hard to find it. Yeah.

[25:01] So, I feel

[25:02] quite like the data is really quite good

[25:05] um

[25:06] in terms of intermittent fasting

[25:08] lowering blood sugar. And in fact,

[25:10] interestingly, the American Diabetes

[25:12] Association mentions intermittent

[25:14] fasting in its guidelines, but it has

[25:15] not yet reviewed the data on blood

[25:17] sugar. So, I'm hoping that they will

[25:19] address that.

[25:20] Um and then for blood pressure, the

[25:22] data's pretty good as well there. There

[25:25] have been two sort of meta-analyses, so

[25:27] these are studies of studies, and they

[25:29] have consistently reported that

[25:31] intermittent fasting seems to lower

[25:32] blood blood pressure. And the effect's

[25:34] about equivalent to taking a single

[25:36] antihypertensive medication, so it's in

[25:38] about the 5 to 10 10-point range. Um

[25:42] there are many fewer studies in this

[25:43] space, but I think the data, you know,

[25:46] this data's pretty solid and is there.

[25:48] Interestingly, almost all the studies um

[25:51] on time-restricted eating that have

[25:52] reported blood sugar or blood pressure

[25:54] benefits had eating windows that by 6:00

[25:57] p.m. or occasionally 7:00. So, maybe

[25:59] earlier in the day is better for those

[26:01] benefits.

[26:01] >> Can we can we double click on that

[26:03] because I

[26:04] I am really aware and mindful of all of

[26:07] the great data around this topic and

[26:10] have tried myself

[26:11] >> Yeah.

[26:12] >> many times to adhere to all different

[26:13] types of fasting protocols. I I must

[26:16] find I must admit the one the only one

[26:18] that I've adhered to with any kind of

[26:20] success is 16:8. Um but and here's the

[26:24] butt.

[26:25] I I find it impossible to eat early in

[26:28] the morning and then stop at like 6:00

[26:30] p.m.

[26:31] Um and I have tried. For me personally,

[26:35] I eat more later in the afternoon and

[26:37] evening than I ever do for breakfast.

[26:39] And it might just be habitual and it

[26:41] probably I could change that, but I just

[26:43] don't feel hungry when I wake up and I

[26:45] and I know other people like that as

[26:47] well.

[26:48] But is the data suggesting that we

[26:50] should flip that round the other way

[26:53] and eat earlier in the day and stop

[26:54] eating.

[26:54] >> see that as one of the million-dollar

[26:56] questions in the field. This is like the

[26:58] question we all need to answer so we can

[26:59] provide the general public with the best

[27:02] advice. So,

[27:03] based on the data we have, the good news

[27:06] is it looks like the time of day that

[27:08] you have your eating window doesn't

[27:09] matter very much for weight loss.

[27:11] >> Huh.

[27:12] >> That's awesome.

[27:13] >> Okay.

[27:13] >> Cuz we know losing weight is amazing for

[27:15] improving your health. Like if you lose

[27:17] your weight, you're going to improve,

[27:18] you know, all kinds of other aspects of

[27:20] your health, whether that's your

[27:21] cardiovascular health, you know, your

[27:23] blood sugar control in the long run.

[27:24] Like weight loss is awesome.

[27:26] There is data suggesting that earlier

[27:29] windows are better for blood pressure,

[27:31] lowering blood pressure, and for

[27:33] lowering blood sugar levels. But it's

[27:35] not at the point where we could where we

[27:37] are confident enough to know for

[27:38] certain.

[27:39] >> Mhm.

[27:39] >> So, this is one of the things we study

[27:41] in my lab cuz I'm very interested in

[27:42] this question. So, I am

[27:45] um I really focus I have one of the

[27:47] largest labs in the world that studies

[27:48] time-restricted eating in humans. And

[27:51] one of the big questions I'm interested

[27:53] in is how much of the benefits of

[27:55] intermittent fasting are due to having

[27:57] that longer fasting period versus the

[27:59] time of day that you're eating. My best

[28:01] guess is some things the daily fasting

[28:04] period matters way more.

[28:06] Like for instance for weight loss and

[28:07] other things the time of day that you

[28:09] eat matters way more. And we just don't

[28:11] know yet.

[28:12] >> Wait, what are the other things?

[28:14] >> Okay, so um there's something called

[28:15] oxidative stress, which is a form of

[28:17] molecular damage in the body. And for

[28:20] that it looks like the daily fasting

[28:21] period might matter more.

[28:23] So, there there things that seem to I

[28:25] mean the data are really preliminary, so

[28:27] I'm not ready to like broadcast to the

[28:29] world, but there we're starting to see

[28:30] some clusters. Like some things matter

[28:33] more. And it may just depend on how

[28:35] strong our circadian rhythms are. So,

[28:37] our circadian rhythms are these 24-hour

[28:39] rhythms in the body. We all have this

[28:41] internal biological clock. This clock

[28:43] makes you better at doing different

[28:45] things at different times of the day.

[28:46] So, for instance, if you're an athlete,

[28:49] the best time of day for competing is

[28:51] the afternoon. And that's because you

[28:52] have the greatest uh muscular strength,

[28:54] the fastest reaction times, the greatest

[28:56] coordination, and and so in the middle

[28:58] of the afternoon.

[28:58] >> that's something to do with core body

[29:00] temperature, I think, or that's

[29:01] certainly an element of it.

[29:02] >> Core body temperature is one way we can

[29:03] measure part of the circadian system,

[29:06] but yeah.

[29:06] >> first. I know most of the world records

[29:09] is set in the athletic world records is

[29:11] set in the early to late afternoon,

[29:13] right?

[29:13] >> Correct. That's exactly the time. Yep.

[29:15] Exactly. Um conversely, in most people,

[29:17] and there are exceptions,

[29:19] um their best blood sugar control's in

[29:21] the morning.

[29:22] And in fact,

[29:23] we you know, the fancy term we'll use is

[29:25] glucose metabolism, has these really

[29:27] strong circadian rhythms. So, we know

[29:30] that that looks like the time of day

[29:32] that you eat, if you eat in alignment

[29:34] with these circadian rhythms that

[29:35] generally make your blood sugar

[29:38] lower in the morning, you're kind of

[29:40] getting a sort of metabolic advantage by

[29:42] eating early in the day. Or in other

[29:43] words, that helps keep your blood sugar

[29:44] levels lower. There's um some really

[29:47] great work out of Israel testing the old

[29:49] adage of eating breakfast like a king,

[29:51] lunch like a prince, and dinner like a

[29:52] pauper,

[29:54] um without changing what times of day

[29:55] you eat, which is awesome. So, this

[29:57] could be another strategy.

[29:58] >> I was just

[29:59] >> Yes.

[30:00] >> scheduling of it. Not the time of day,

[30:03] so

[30:03] >> Correct. Yeah, so for instance,

[30:05] >> in the earlier meal, right?

[30:06] >> Correct. Yeah, so for instance, in these

[30:08] studies, they'd have people typically

[30:09] about 50% of their daily calories for

[30:11] breakfast,

[30:13] and then I think it's something like

[30:14] roughly

[30:15] 30%

[30:17] maybe for lunch and 20% for dinner, or

[30:20] they'd have them do the opposite.

[30:22] And they lost significantly more weight.

[30:25] And not only did they lose more weight,

[30:27] but they were less hungry, which I find

[30:29] amazing, right? Cuz if you're losing

[30:30] more weight, shouldn't you be more

[30:31] hungry? But they were actually less

[30:33] hungry than the control group that was

[30:34] struggling to lose weight. Um and it

[30:36] also lowers your blood sugar levels. Um

[30:39] >> Wait, they were eating more earlier in

[30:41] the day.

[30:41] >> Yes.

[30:42] >> They lost more weight and they felt less

[30:44] hungry.

[30:44] >> Correct.

[30:46] Cuz cuz to me I mean like that's I mean

[30:47] if you think about it from the flip

[30:48] side, that means the group that was

[30:50] eating more for dinner were struggling

[30:51] to lose weight and they were hungrier.

[30:54] This is like the one-two punch in the

[30:55] opposite direction. Yeah.

[30:57] And so we there's not as much

[30:59] Ironically, there's not as much Maybe

[31:01] it's I don't know if it's ironic, but

[31:02] there's less data on the time of day of

[31:05] food intake. The data we have is very

[31:06] good. It's very consistent. There are

[31:07] not as many studies. We have far more

[31:09] studies on intermittent fasting.

[31:11] So I mean I think this is another meal

[31:13] timing strategy. Like if you have people

[31:15] who are like, "I can't do intermittent

[31:16] fasting, but I'm willing to change the

[31:19] timing of what I eat in some capacity."

[31:21] Or maybe I like I have to have dinner,

[31:23] right?

[31:24] >> Yeah. Yeah. Yeah.

[31:24] >> And then I would say try to make

[31:26] breakfast and/or lunch your largest

[31:28] meals of the day. Make dinner your

[31:30] really healthy meal. Like maybe that's

[31:32] your salads and your fruit and

[31:33] vegetables or it's like smaller portion

[31:34] sizes. Um cuz there is good data

[31:37] suggesting you'll get benefits. So my

[31:39] general approaches, I don't think

[31:41] intermittent fasting is for everyone.

[31:42] >> Mhm.

[31:43] >> Um I think sort of people's lifestyle

[31:44] and behavior matter a lot. And so I

[31:47] think it's really important to take all

[31:48] those factors into account.

[31:50] And so but I do believe there's

[31:52] something in meal timing for everyone.

[31:54] And it could be as simple as, you know,

[31:56] even like I'm not going to eat 3 hours

[31:58] before bedtime.

[31:59] Awesome. You know, cuz it takes it takes

[32:02] people on average 4 to 6 hours to digest

[32:04] a meal. So if you're going to bed every

[32:06] night while you're still digesting your

[32:07] food and um you know, maybe you eat like

[32:11] 2 hours before bedtime, your blood sugar

[32:12] levels are going to be elevated for

[32:14] longer and there's data suggesting that

[32:16] that

[32:17] um makes it harder for your body to

[32:19] break down and burn fat for fuel. Um so

[32:22] so there's some negative things there.

[32:24] >> I'm doing this completely wrong myself.

[32:27] >> Yeah.

[32:27] >> Um even when I am practicing the

[32:29] fasting.

[32:30] >> And

[32:32] I think that is more

[32:34] just discipline, but I I find it really

[32:36] difficult after like a long day at work

[32:39] to get home and you know, I'm not by the

[32:41] time I get home, I haven't got 3 hours

[32:44] >> Yeah.

[32:44] >> before I go to bed.

[32:45] >> Yeah.

[32:45] >> And I think a lot of people are probably

[32:47] in that scenario certainly with

[32:48] families. And probably find it would

[32:51] find it really difficult regardless of

[32:53] the evidence to

[32:54] >> Yes.

[32:54] >> not eat for 3 hours.

[32:57] I also find and I might be on my own

[32:59] when I say this

[33:01] that

[33:02] as soon as I start eating in the day, I

[33:04] just feel like the floodgates, right?

[33:05] I'm I just then I just want to snack all

[33:07] day until I go to bed.

[33:09] And and so I wonder if there is any

[33:10] science to that or that is just me not

[33:13] being disciplined enough. But I feel

[33:15] like when I delay the breaking of the

[33:17] fast in the morning

[33:19] then that's my only hope of fitting it

[33:21] within a reasonable window.

[33:23] >> Yeah.

[33:23] >> So I guess my my point is or my question

[33:26] is

[33:27] all things considered

[33:30] would you say that even with that data

[33:32] >> Yeah.

[33:33] >> given how beneficial it appears to

[33:35] restrict

[33:36] >> Yes.

[33:36] >> of food we eat to

[33:37] within a certain window

[33:39] regardless of the the way you

[33:40] choreograph it, there's still probably a

[33:42] big upside even if it is done later in

[33:45] the day.

[33:46] >> Yeah, I absolutely. And what I like to

[33:48] do

[33:49] none of this stuff is set in stone. Like

[33:51] we may get a amazing clinical trial that

[33:52] answers this definitively. Maybe one of

[33:54] our studies will or someone else's will.

[33:56] >> I really hope so.

[33:57] >> But I like to rank where I think the

[33:59] data is going and then let people pick.

[34:02] Um so I would say if you have all the

[34:04] motivation in the world, you don't have

[34:06] obligations like kids or things like

[34:08] that and you want to go the full 9

[34:10] yards, my guess is you'll get the most

[34:12] benefit from doing time restricted

[34:13] eating early in the day. I'd recommend

[34:15] an 8-hour window or or less. Sort of as

[34:18] early as you're willing to move

[34:19] breakfast. For folks who are really

[34:21] motivated, they can go to bed on an

[34:22] empty stomach. That was definitely me

[34:24] before having kids and I did that for

[34:26] years. My sweet spot was like a 6 to

[34:27] 8-hour window. I'd start at 8 8:00 a.m.

[34:30] and then finish between 2 to 4 just

[34:31] depending on my meeting schedule. Loved

[34:33] it, felt great, love my energy levels.

[34:36] Um I think most people are not willing

[34:38] to do that.

[34:38] >> Yeah.

[34:39] >> Um my second choice would probably, you

[34:42] know, I think this is probably evolved

[34:44] over time.

[34:45] My second choice at the moment would

[34:46] probably be a tie between doing inner

[34:49] intermittent fasting or the time

[34:50] restricted eating later in the day

[34:52] or eating breakfast like a king, lunch

[34:55] like a prince, and dinner like a pauper.

[34:56] And I don't know what's best at the

[34:57] moment.

[34:58] >> Yeah. What do you do now?

[34:59] >> Um I'm sort of like closer to 9-hour

[35:02] window

[35:04] um with kids and just being really busy

[35:06] with like moving my lab

[35:07] >> Yeah.

[35:08] >> uh to Harvard, but um I'd like to get

[35:10] back to an 8-hour window. I'm going to

[35:13] play it So so far it has a not really

[35:15] impacted my ability to have dinner. Like

[35:17] I got a 2-year-old, like I spend half my

[35:20] meal trying to get her to eat, so it's

[35:21] like no

[35:22] big deal.

[35:23] Um but 16 to 18 hours is my sweet spot,

[35:26] you know, that's the thing I really

[35:27] like. So I'm kind of playing it by ear.

[35:28] I definitely like if I, you know, I

[35:31] don't We'll see what I do long-term, but

[35:33] at the moment I'm able to do it without

[35:35] the kids or without it being an issue.

[35:37] But if it is an issue, like, you know,

[35:38] family family comes first, right?

[35:40] >> yeah.

[35:40] >> I'll I'll still use the broader

[35:41] principles. So for me, I eat about 75 to

[35:46] 80% of my calories before noon.

[35:48] And my body is like really adapted to

[35:50] that. So I get I mean, talking about you

[35:52] saying some things are easy and hard,

[35:54] >> Mhm.

[35:54] >> I suspect, and we don't have great data

[35:56] on this, that people adapt to what they

[35:58] do in the long term.

[35:59] >> Yeah, yeah, yeah.

[36:00] >> And we have found that when people first

[36:02] change their eating schedules in our

[36:03] studies, they say it's it's actually

[36:05] quite hard.

[36:06] But after a few weeks, they start

[36:08] adapting, and then many people are

[36:09] saying it's a non-issue.

[36:11] >> Really?

[36:11] >> Yes, and

[36:12] >> so much of this is about adherence as

[36:15] well, right? Like

[36:16] >> Yes.

[36:16] >> if there was a slight edge to be had

[36:18] each day, if you can compound those days

[36:20] over time because it fits into your life

[36:22] in a way that doesn't, you know, suck

[36:24] the joy out of it, then then long-term I

[36:26] would I would

[36:28] imagine that that's going to be the most

[36:29] beneficial. I think the nice thing for

[36:31] listeners to know as well is that when

[36:33] you say we don't know for sure about one

[36:34] of these things.

[36:35] >> don't know.

[36:36] >> Which is not really what we're led to

[36:37] believe with you know, we sometimes will

[36:39] see a headline saying you know, skip

[36:41] breakfast and you'll live longer for

[36:43] example and that's not yeah, yeah, and

[36:45] that's not really how the science works.

[36:47] >> I think breakfast skipping has been so

[36:49] controversial because um

[36:52] what's really interesting there's work

[36:53] out of Japan that shows that about half

[36:55] of people who skip breakfast eat dinner

[36:57] late.

[36:58] And we know eating dinner late isn't is

[37:01] not you know, not great. Um but the

[37:03] other half of people who skip breakfast

[37:05] eat dinner at a normal time so they're

[37:06] doing intermittent fasting.

[37:08] >> Mhm.

[37:08] >> So you're lumping together two very

[37:10] different groups of people and also in

[37:12] the folks who skip breakfast regardless

[37:15] of whether they eat eat dinner late,

[37:16] you're going to have more people doing

[37:17] shift work.

[37:18] And we know shift work increases your

[37:20] risk of several chronic diseases,

[37:22] cancer, diabetes, hypertension, etc. And

[37:25] a lot of these studies don't take that

[37:26] into account. Like you got to have these

[37:28] sort of clean data sets to answer answer

[37:30] these questions.

[37:32] Um

[37:33] I've lost my train of thought but let me

[37:34] go back to one of so

[37:37] I said earlier like the late time

[37:40] restricted eating and eating early in

[37:41] the day would be my second choices

[37:43] probably tied based on the quality of

[37:44] evidence. I'd say third would be a

[37:46] simple rule of like don't eat within

[37:48] three to four hours of bedtime or

[37:50] whatever you can make that rule be.

[37:52] Um just because you're going to like

[37:55] dinner is the time of day when you have

[37:57] the worst blood sugar control.

[37:59] So the less you can kind of less stress

[38:01] you can put on your system, the better.

[38:03] Stress is not quite the right word but

[38:05] you know, I think you get my general

[38:06] point. And I would say third if you're

[38:08] just like I can't do any of that, make

[38:11] dinner a healthy meal. And the reason

[38:13] why

[38:14] is cuz if you give someone a healthy

[38:15] meal and junk food meal in the morning,

[38:18] there is a difference in blood sugar but

[38:20] it's you know, on the smaller side. If

[38:22] you give that's that same healthy meal

[38:25] and a junk meal late in the day, there's

[38:26] a much bigger difference in in blood

[38:28] sugar. In other words, that junk food

[38:30] meal later in the day is worse for your

[38:31] body.

[38:32] So, if you can still at least make

[38:33] dinner your healthiest meal of the day,

[38:35] you should get some improvement.

[38:37] >> This is going to be my takeaway from

[38:39] today's conversation. Whatever else we

[38:41] talk about. I often will eat myself to

[38:43] sleep. And not not just like lots of

[38:45] volume of food. I don't think I overeat,

[38:48] but that's often the last thing I do

[38:50] before I go to bed. So, I'm going to try

[38:52] this this evening.

[38:53] >> There are a small number of studies,

[38:55] too, that show where they've tested like

[38:57] regardless of how long what's called the

[38:59] eating window was. So, they tested the

[39:01] same eating window early versus late in

[39:02] the day that do find an impairment in

[39:04] fat burning at night. So, I think that

[39:06] is not a great deal

[39:08] not a not a great thing to have. And

[39:09] there also some of the genes that are

[39:11] involved in

[39:14] in uh fat burning and and just generally

[39:17] regulating what we call our energy

[39:18] metabolism or you think of it as your

[39:20] metabolism.

[39:22] The genes that sort of promote fat

[39:23] storage are sort of

[39:25] you know, they are increased when you

[39:27] tend to eat later in the day. But again,

[39:28] these are broader principles. I think

[39:30] people should do what they can and

[39:32] that's what I would hope they take away

[39:33] from this meal.

[39:34] >> the good thing is that especially with

[39:36] something like this that's not doesn't

[39:37] cost anything, right? It costs time and

[39:39] effort, but if anything actually you

[39:41] probably gain back some time because of

[39:43] you know, less less decision paralysis

[39:46] or decision fatigue throughout the day,

[39:48] which probably actually contribute to

[39:50] the data is that like if you're not if

[39:52] it's just a I can't eat outside of this

[39:54] window, there's less likelihood that

[39:56] you're snacking or filling time with

[39:59] boredom eating or comfort eating. So, I

[40:00] imagine that actually impacts that. Can

[40:03] I ask you a layered question?

[40:05] >> Yes.

[40:05] >> Um so,

[40:08] Will and I um who's our chief science

[40:10] officer and who's actually on the

[40:11] podcast, he's here today.

[40:13] Um we went to a a conference not so long

[40:15] ago

[40:16] and amongst the talks that someone put

[40:19] graph up about emerging therapeutics

[40:22] molecules that that are looking to be

[40:25] sort of promising gero-protectors. So,

[40:27] things that hopefully in at some point

[40:29] will get proven safe and effective for

[40:32] humans, but we're we're some way off

[40:34] that right now and layered the data we

[40:36] have so far as a as a lifespan

[40:39] intervention. So, something that could

[40:41] help increase the number of years we

[40:42] live and healthy years one would hope.

[40:46] And then

[40:47] on the next side layered over

[40:49] intermittent fasting and the impact that

[40:51] has had on lifespan or markers of

[40:53] longevity and it beat pretty much all of

[40:55] them, right? Or it certainly was

[40:57] competitive with all of those things. Um

[41:00] what would and this is the first part of

[41:02] the question.

[41:04] Are there markers that we associate with

[41:06] living a longer healthier life that we

[41:08] see improve when people adhere to this

[41:10] at least in the studies that you're

[41:12] aware of?

[41:13] >> Yeah. Yeah, so I'm going to answer to

[41:15] this question a little longer way cuz I

[41:17] can provide more important context. So,

[41:19] um we have pretty good data now that in

[41:21] most studies in animals that

[41:23] intermittent fasting extends lifespan.

[41:24] There are some exceptions.

[41:26] For now, there are various types of

[41:28] intermittent fasting that was studied in

[41:30] animals, but time restricted eating the

[41:32] data is really quite consistent. The way

[41:35] in which it looks like it extends

[41:36] lifespan is by increasing something

[41:38] called autophagy,

[41:39] which is like kind of cellular recycling

[41:41] of worn out and damaged proteins. And

[41:44] the reason why we think autophagy is

[41:45] involved and there are not many studies

[41:47] of autophagy. Yeah, so it's like a

[41:48] cellular recycling program.

[41:51] The reason why we think autophagy is

[41:52] involved, if you do something called

[41:54] knocking out those genes. So, if you

[41:56] kind of block them from doing what they

[41:58] should be doing um and you prevent that

[42:00] increase in autophagy, you don't get the

[42:02] lifespan extension. There are not many

[42:04] studies on this, but I can think of

[42:05] three studies that have done this and

[42:07] done this well suggesting that at least

[42:09] the cellular recycling is involved. So,

[42:12] one of the ways in which I my guess

[42:14] intermittent fasting is working is by

[42:17] a very simple weather level just giving

[42:19] your body more time to rest and

[42:20] recuperate. Like, I think we need these

[42:22] contrasts in life. Like,

[42:24] >> Mhm.

[42:25] >> activity and rest, you know, light and

[42:27] darkness and so forth. Um feeding

[42:30] fasting. And that's how the body sort of

[42:31] optimally functions. You need the

[42:33] challenge and then you need the

[42:35] recovery. Challenge and recovery.

[42:37] Um and so, I think that's a big part of

[42:40] what's going on behind the scenes. So,

[42:42] if you look at autophagy as the function

[42:44] of the number of hours someone's been

[42:45] fasting, you see you tend to see an

[42:47] increase in humans around kind of like

[42:50] 11 to 13 hours and and it goes up. Um

[42:53] so, I think that's one of the main

[42:55] mechanisms. So, for me

[42:58] the impact of intermittent fasting on

[42:59] aging is hugely exciting.

[43:01] Now, I know other people have talked

[43:03] about the profound effects of exercise

[43:06] on lifespan, but a lot of that data is

[43:09] epidemiological.

[43:11] And my concern is somewhat So, you often

[43:13] will hear people say VO2 max is like the

[43:15] best predictor of lifespan.

[43:17] >> Mhm.

[43:18] >> Uh as a scientist, I don't buy it.

[43:20] And here's why. One is epidemiological

[43:22] data. Two, the way the data is often

[43:25] presented, I think they take the bottom

[43:27] 25%

[43:29] and compare it to like the top X percent

[43:31] of people. Well, if you picking the

[43:32] bottom 25%, you're going to have people

[43:34] who are bedridden in there and who are

[43:36] on death's door, right? So, and then in

[43:38] animals, where they've tested exercise

[43:41] versus diet for extending lifespan, diet

[43:43] has had the bigger effect than exercise.

[43:45] I could be wrong, but let me just say I

[43:47] just don't I don't accept that as as a

[43:50] truism. Um so, I think, you know, diet

[43:53] seems to play a big role. Now, there are

[43:55] all all kinds of other things that play

[43:57] a big role. So, I don't know if diet

[43:58] pro- plays the predominant role. But my

[44:01] guess is that we can probably that

[44:03] having a healthy diet or doing

[44:07] intermittent fasting um is definitely

[44:09] going to improve health span and life

[44:11] span and we do see that in animal

[44:13] studies. Um there's some data suggesting

[44:16] that male mice benefit more than female

[44:19] mice in terms of life span expansion

[44:21] with intermittent fasting

[44:22] but there much bigger differences

[44:24] between male and female mice than there

[44:26] are male

[44:26] >> Yeah.

[44:27] >> men and women or humans.

[44:29] Um

[44:31] so I take some of it with a grain of

[44:32] salt. In the studies that don't find as

[44:34] impressive results for life span

[44:36] expansion in females do find impressive

[44:38] results for health span extension in

[44:40] females. So I I think to me this is I

[44:42] think going to be a core component of

[44:44] healthy aging.

[44:45] >> Yeah.

[44:45] >> We talked kind of earlier about you know

[44:47] behavioral factors cuz I don't study

[44:49] behavioral factors but I think they're

[44:50] super important. Like what can you

[44:52] sustain in the long term? That's what

[44:53] you should do.

[44:54] >> Um but I think there's also going to be

[44:56] some inter-individual or there's going

[44:58] to be like individual to individual

[45:00] variation like metabolism and things

[45:03] like that. So

[45:05] in obesity research we often think that

[45:07] some people have greater what's called

[45:09] metabolic flexibility than other people.

[45:11] So meaning in other words some people

[45:13] get to that fat that burning state or

[45:15] easier than others. So one of the things

[45:17] I'm excited about studying in the future

[45:19] is figuring out like what should be

[45:21] someone's personalized

[45:22] >> Yeah. Yeah.

[45:23] >> eating window?

[45:24] What should it be? Like how many hours

[45:25] should they fast? Why do some people

[45:27] seem to benefit more than others? Is it

[45:29] because some people are sticking with

[45:31] the diet better than others or is there

[45:32] something about their metabolism that

[45:34] makes it better or worse?

[45:36] Um

[45:38] yeah and and there could be timing

[45:39] things. Like we know there's

[45:42] So there's more than one circadian

[45:43] rhythm in the body

[45:45] um

[45:47] we know some people tend to be more like

[45:48] morning types than other people tend to

[45:50] be light types. Does this affect

[45:53] you know how like the time of day that

[45:55] they should eat the length of their

[45:56] fasting period? So I think they're all

[45:57] kinds of really important questions that

[45:59] we need to ask and that's one of the

[46:00] places I'm excited for the field to go

[46:02] in the future to figure that out.

[46:04] >> exciting, right? Because that get

[46:06] getting that

[46:07] and we call that sort of phenotyping,

[46:09] like testing across these different

[46:11] systems, which is really the true north

[46:13] of what what we're doing here is like

[46:14] how do we get more granular data about

[46:17] our biology and our genetics and our

[46:19] preferences even and then apply that to

[46:21] this evidence that that we know

[46:23] works. It's good that there's an unlock

[46:25] there for all of us. It's just figuring

[46:27] out what that is and like and and how to

[46:29] do that with consistency.

[46:30] >> Correct. Yeah, there was a nice study

[46:32] out of Spain that showed that people who

[46:34] got the same weight loss intervention,

[46:36] those who had stronger circadian rhythms

[46:38] lost more weight.

[46:38] >> Yeah, I can imagine.

[46:39] >> So now time-restricted eating is a way

[46:42] to maybe improve some of those circadian

[46:45] rhythms or some aspects of the circadian

[46:47] system. So it may be like the

[46:49] combination of a bunch of different

[46:51] strategies we can, you know, like help

[46:53] people optimize weight loss, but I think

[46:55] there's a lot to be done to figure out

[46:56] like

[46:57] who benefits most, how do we design

[47:00] these interventions so that they're

[47:01] sustainable, um and how much tailoring

[47:04] we need to do.

[47:05] >> me as an individual? And I think that's

[47:07] the challenge for all of us when we're

[47:08] consuming content about healthspan,

[47:12] lifespan, these these terms that are

[47:13] being thrown around with so many

[47:14] different definitions is what does that

[47:16] mean for me?

[47:17] >> Right.

[47:18] >> Or what does that mean for me today is

[47:19] what we really need to figure out. Hey,

[47:20] I'm going to move on to the second part

[47:22] of my question.

[47:23] >> Okay. Oh, yes.

[47:23] >> Um and I'm going to push back on the VO2

[47:26] comment if you don't mind. The reason

[47:27] being I think

[47:29] the second part of the question is, you

[47:30] know, with nutrition

[47:33] research in general, which is

[47:34] notoriously difficult

[47:36] >> Yes.

[47:36] >> to do well, right? We have, you know,

[47:38] lots of them are observational studies,

[47:41] also epidemiological studies in large

[47:43] part. There is um

[47:45] huge bias when it comes to

[47:47] self-reporting and that we've seen that

[47:49] the the variation in self-reporting is

[47:51] is wildly broad with people,

[47:55] >> Yeah.

[47:55] >> you know, um actually telling the truth

[47:57] about what they're eating and the timing

[47:59] especially.

[48:00] And and so

[48:02] and then when it comes to animal models,

[48:04] you know, the the metabolism of a mouse

[48:06] is different to a human. Mice typically

[48:09] will just eat over a much broader,

[48:12] larger window if they're given the

[48:13] opportunity to. And so I think

[48:16] and this is why it's so exciting to

[48:17] speak to you because your study studying

[48:20] actually what happens in humans under

[48:21] controlled and situations. But even

[48:23] then, like how does that apply over the

[48:26] long term? Right? And I think

[48:28] the trouble with applying any of this

[48:30] data to lifespan is that's also

[48:33] >> Yeah.

[48:34] >> notoriously difficult to measure because

[48:36] we can't wait decades to figure that

[48:38] out.

[48:39] And so I think you know, how do we

[48:42] solve for that with nutritional research

[48:44] given that as the end consumer, I don't

[48:46] know the difference between some

[48:48] observational study where there's a huge

[48:51] user bias and then a media bias and a

[48:53] study bias.

[48:56] And a lot of hype. How do I determine

[48:58] the difference between those because I

[49:00] think for exercise we do have more data

[49:02] on on people or less discord at least.

[49:05] >> We definitely have more agreement on

[49:07] >> Yeah.

[49:08] >> I just think nutrition

[49:09] >> I don't think it's a zero-sum game. I

[49:11] think you have to do

[49:12] >> Oh no, I think you need both. And in

[49:13] fact, I would counter argue play you

[49:16] devil's advocate to myself which is I

[49:17] think exercise is tremendously important

[49:20] for health span.

[49:21] >> Yeah.

[49:21] >> Right. Like if you're having a longer

[49:22] life that's not a healthier life

[49:24] >> Yeah.

[49:25] >> you lose, I think.

[49:26] >> Yeah, and I think the one really good

[49:27] point you make certainly about VO2 like

[49:29] there's there seems to be like just

[49:31] three or four tests or metric that get

[49:33] banded around as like the gold

[49:35] [laughter] standard for everyone every

[49:36] time and and VO2 is one of those things.

[49:39] I think it's really important but we

[49:40] shouldn't overreach there either.

[49:42] >> Yeah, yeah.

[49:43] Um all great questions. I don't know how

[49:45] to consumer navigates this. My hope is

[49:49] that the dietary guidelines for

[49:50] Americans take up this topic and it

[49:52] becomes a nutrition guideline. I know

[49:54] they were considering it a couple years

[49:56] ago.

[49:57] Um my guess is they did not move forward

[49:59] cuz I didn't hear further.

[50:00] But that may change in the future cuz it

[50:02] depends on how many clinical trials

[50:04] there were. Like when I got started,

[50:05] there were like a dozen clinical trials

[50:07] on intermittent fasting and we're now up

[50:09] to over 225. It's a big increase.

[50:12] Um when I started giving talks, I was

[50:14] like, here are 20 studies and now I'm

[50:15] like I can barely really discuss them

[50:17] all which is awesome.

[50:18] Um

[50:20] I I think we

[50:21] you know, it's through our conversation

[50:23] we shared a lot of practical tips. I see

[50:25] these as principles. Like what can you

[50:26] do in your daily life and then you

[50:28] figure out what you can do.

[50:30] Um

[50:32] But yeah, I mean this is why I think

[50:33] it's important to listen to scientists

[50:35] cuz things get over over hyped. I mean

[50:37] one of the reasons I was excited So by

[50:40] the way, I've turned down all all other

[50:42] companies that have ever approached me

[50:44] um to be involved in fasting apps. And

[50:46] part of the reasons for for that is I

[50:48] wanted to always have the ability to

[50:50] think independently and change my mind.

[50:52] >> Yeah.

[50:53] >> And what I like that's different about

[50:55] what you're doing at Wonder Health is

[50:56] you're trying to assemble the best

[50:58] scientists in the world and have them

[51:00] tell you

[51:01] what, you know, is actually true of the

[51:03] literature. So for instance, I'll give

[51:05] this example to people.

[51:06] I'll get asked all the time because I'm

[51:08] a nutrition researcher, what's the

[51:09] latest on protein? I have no idea. And

[51:12] part of that is realizing like you have

[51:14] to know the research out there in such

[51:16] great depth

[51:18] to really know what's going on.

[51:20] So for instance, there was a big

[51:22] headline

[51:23] I think it's maybe a year or two ago

[51:25] that intermittent fasting increases the

[51:28] death rate from cardiovascular disease

[51:30] by like 91 or 92

[51:32] percent. And this was research that had

[51:34] not been published but was presented at

[51:36] a meeting.

[51:37] And a bunch of us who do intermittent

[51:39] fasting research, um we reviewed the

[51:41] research and there were all kinds of

[51:43] problems and flaws. So for instance, the

[51:45] the group that was the intermittent

[51:46] fasting group. Um

[51:49] First of all, there are far more smokers

[51:52] in that group. There are far more

[51:54] individuals from minority backgrounds,

[51:56] lower SES, like they were like lower

[51:59] physical activity levels. The groups

[52:00] were just not matched, which since this

[52:03] is an epidemiologic study, you have to

[52:04] have that matching.

[52:05] >> What's the time for that, Courtney?

[52:07] There's a word for that, isn't there?

[52:08] >> It's confounders.

[52:09] >> Confounders, yeah.

[52:10] >> Yeah. So, there are all these

[52:11] confounders. They create I mean, we

[52:13] would call it like a spurious

[52:14] association, but like a false belief of

[52:17] what's going on. And these are not small

[52:19] differences. These were dramatic

[52:21] differences.

[52:23] Um second, what the authors didn't

[52:25] advertise is they didn't actually

[52:27] calculate the eating window. They

[52:28] calculated the average of the eating

[52:29] duration, which may sound like a small

[52:31] difference, but it's a big one. And the

[52:33] reason why it's a big one is

[52:34] they counted people as doing 8-hour

[52:36] time-restricted eating if they ate over

[52:38] 12 hours one day and 3 hours the next

[52:40] day, cuz it averages out less to that.

[52:42] >> Sure, yeah.

[52:43] >> So,

[52:44] we actually looked at their data. Yeah.

[52:46] Sounds like I like like I'm splitting It

[52:47] sounds like I'm splitting hairs, to be

[52:48] honest. But when I looked at their data,

[52:50] 75% of people in their time-restricted

[52:54] eating group did time-restricted eating

[52:56] on one day, but not the other.

[52:58] And so, what they're actually measuring

[53:00] is erratic eating.

[53:02] And so, I think the punchline should

[53:04] have been erratic eating increases the

[53:07] risk of death. But interestingly, if you

[53:08] did limit it to people who consistently

[53:11] ate in an 8-hour window on both days,

[53:13] the association vanished.

[53:14] >> Of course.

[53:15] >> Amazingly, right?

[53:16] >> why it's so difficult to know what

[53:17] >> No, that Yeah. And And there There are

[53:19] all There are all sorts of like small

[53:20] details, too, like as a nutrition

[53:23] researcher, the most common reasons that

[53:25] it looks like someone does intermittent

[53:26] fasting is they didn't fill out the food

[53:28] record.

[53:29] >> Of course, yeah.

[53:30] >> that looks like is they've reported two

[53:31] of their three meals of the day. Looks

[53:33] like intermittent fasting, but what

[53:34] you're really measuring is people who

[53:36] are on top of their stuff and people who

[53:37] aren't. And we generally find in any

[53:39] clinical trial people who are more on

[53:40] top of their stuff do better.

[53:42] So, there are the all these other

[53:43] details and then they found that

[53:45] actually the 8-hour eating window is

[53:46] correlated with a lower risk of

[53:48] hypertension and type 2 diabetes, but

[53:49] they buried that finding cuz that didn't

[53:51] fit their inflammatory

[53:52] >> Yeah.

[53:52] >> narrative.

[53:53] >> I think this is why we do need to speak

[53:54] directly to the people that are doing

[53:56] the research, right? Because you will

[53:57] get

[53:58] >> Yes.

[53:58] >> in the same publication will see, and I

[54:00] mean media publication, will see, you

[54:02] know, intermittent fasting adds decades

[54:05] of functional years to your life and

[54:06] then a year later be like intermittent

[54:08] intermittent fasting kills you.

[54:09] >> why we look at the consensus, right?

[54:11] This is why we don't If you're weighing

[54:13] a single study, I mean actually this is

[54:15] a good rule of thumb. If you're

[54:17] hinging on a single study, then you're

[54:20] probably making a mistake.

[54:22] But if you're looking at the body of

[54:24] research, you're going to find 75% of

[54:26] studies say one thing, 25% say another

[54:28] thing, the 75% is probably right.

[54:30] Right.

[54:31] >> explain to the listeners like why like a

[54:33] meta-analysis of randomized control

[54:35] trial would feel more valuable than a

[54:37] than a single study and and how they

[54:39] they could probably

[54:42] when observing these headlines or

[54:43] articles might be able to use that rule

[54:45] of thumb.

[54:46] >> Yeah, so so in general with

[54:48] epidemiologic studies, so these are

[54:50] studies where you

[54:52] just ask people, "What are you doing?"

[54:53] And then you just follow up with what

[54:54] they're doing long term. So, we call

[54:56] these like observational studies. So, we

[54:58] don't change their behavior, we just see

[54:59] what people are doing and then and

[55:01] follow them long term. Or some many

[55:02] times we just say, "How does your health

[55:04] look right now?"

[55:04] >> Mhm.

[55:05] >> Is there all kinds of

[55:07] we call them like reverse associations,

[55:09] but things that would make you come to

[55:10] the wrong conclusion. A very famous

[55:13] example is among like never smokers and

[55:15] never drinkers, sometimes the risk of a

[55:18] disease can be much higher cuz these are

[55:20] people who, you know, for instance,

[55:21] never drinkers, you have a lot of people

[55:23] who

[55:24] had alcoholism or drank a lot and now

[55:27] are abstaining.

[55:27] >> Mhm.

[55:28] >> And so, because they have this history,

[55:30] they'll bring up the death rate in that

[55:32] group.

[55:33] >> I think the same applies to like red

[55:35] meat as well, right?

[55:36] >> if you have a randomized control trial,

[55:38] you bring people in, you have them stop

[55:39] the behavior to see their health

[55:40] improves. That's why it's so important

[55:42] to do clinical trials. So, we always say

[55:44] you can't prove

[55:45] something causes another thing from

[55:47] epidemiologic studies. It They are

[55:49] useful

[55:50] cuz they tell us what questions to ask

[55:52] and they can confirm things we see in

[55:55] randomized studies.

[55:55] >> groups, I see. Yeah.

[55:56] >> Exactly. But, yeah. So, the things I

[55:58] tend to trust are large clinical trials

[56:01] um and then meta-analyses of clinical

[56:03] trials.

[56:04] >> Could you maybe give a definition of

[56:05] meta-analysis? Like what what cuz there

[56:08] will be people listening that don't

[56:09] really know what that means, I guess.

[56:10] >> Absolutely. So, meta-analyses are where

[56:12] you go out and look at all the research

[56:14] in an area. So, say it's weight loss.

[56:17] You take all the results and you kind of

[56:19] average them together to see what the

[56:20] sort of average effect is weight for

[56:22] weight loss across all these studies.

[56:24] >> an unbiased look at the research effect.

[56:26] >> so you're averaging over studies where

[56:27] there was no effect, studies that where

[56:29] there was an effect, and you're saying

[56:30] what's the net effect of all this.

[56:32] >> Love it.

[56:32] >> Where does the truth lie?

[56:34] >> Hey, can I Can we switch it up a little?

[56:36] I want to ask you about some specific

[56:39] cases and how they relate to

[56:41] intermittent fasting.

[56:42] >> Yes.

[56:42] >> The first is Is there like Are we seeing

[56:44] gender differences um

[56:47] and and impact on hormonal or or

[56:49] menstrual cycle? I I I think there's

[56:51] been some compelling data there, but I

[56:53] don't know.

[56:54] >> Yeah. Yeah, we actually I I was tapped

[56:56] to give a a talk on women and

[56:58] intermittent fasting in Germany about a

[56:59] year ago. So, I've reviewed all that

[57:01] literature. Um it was really

[57:02] interesting. Prior to that, I had maybe

[57:04] about half a dozen women came up to me

[57:06] and say say I stopped intermittent

[57:07] fasting because this influencer told me

[57:10] it was bad and it was messing with my

[57:11] hormones. So, we actually reviewed all

[57:13] the data and there's absolutely no

[57:15] negative effects on hormones.

[57:17] There's also a concern. So, the one

[57:19] thing that intermittent fasting seems to

[57:20] affect, it seems to slightly reduce

[57:22] testosterone levels in both men and

[57:24] women.

[57:25] We don't see any differences, negative

[57:27] effects on strength. There are a number

[57:29] of studies in people who are either

[57:32] habitual resistance trainers, meaning

[57:34] they've been doing resistance training,

[57:36] or are new to resistance training.

[57:38] And in all those studies, we don't find

[57:40] that intermittent fasting reduces muscle

[57:42] strength,

[57:43] uh muscle cross-sectional area, muscle

[57:46] accretion, or anything like that. So, it

[57:47] seems to have no effect, which is great.

[57:49] Nothing negative, nothing positive.

[57:51] Um but there is this reduction in

[57:52] testosterone levels.

[57:54] And there's an increase in something

[57:55] called sex hormone um

[57:58] binding

[57:58] >> binding globulin

[57:59] >> globulin. Thank you. Uh I just want to

[58:01] make sure I didn't say the words in the

[58:02] wrong order. Um

[58:04] And those are the only two hormones we

[58:05] see that are affected. We don't know yet

[58:07] whether there's anything negative with

[58:09] that. We don't see signs that that

[58:11] translates into

[58:14] other negative aspects of health, but

[58:15] it's certainly something that that um

[58:17] happens.

[58:19] Um

[58:21] We don't see any uh negative effects in

[58:22] women.

[58:24] Um we recently did a did a study, it was

[58:26] just accepted today, where we looked at

[58:28] whether there are differences, thank

[58:29] you, between men and women, and we find

[58:30] no differences between men and women.

[58:32] So, and there was another nice large

[58:34] study published in Nature Medicine, also

[58:36] no difference between men and women for

[58:38] weight loss and other aspects of health,

[58:40] which is different from the animal

[58:41] literature. This is again why I I don't

[58:43] Animal literature is super important for

[58:45] me as a scientist, but I don't over

[58:46] weight it.

[58:47] >> Yeah.

[58:48] >> Um

[58:49] And then the other question I get asked

[58:51] about is menopause.

[58:52] >> Mhm.

[58:53] >> And

[58:55] um

[58:56] all the data, there are probably about

[58:57] half a dozen studies that have looked at

[58:59] postmenopausal women either in

[59:01] comparison to premenopausal women or in

[59:03] general,

[59:04] and if anything, postmenopausal women,

[59:06] they benefit just as much from

[59:08] intermittent fasting, if not slightly

[59:10] more, in terms of weight loss. So, the

[59:12] good news is it looks like it's great

[59:14] for postmenopausal women, too. But I

[59:16] don't see any Aside from the small

[59:18] decrease in testosterone, I don't see

[59:20] any negative effects on sex hormones in

[59:22] women. And there was even one study

[59:24] showing that it decreased um

[59:26] PMS symptoms. So.

[59:28] >> Any anything on fertility?

[59:30] >> No. Um there's one study looking at

[59:34] eating breakfast like a king, lunch like

[59:36] a prince, and dinner like a pauper, and

[59:37] they found an improvement in fertility

[59:40] in women with PCOS. It doubled the

[59:42] number of women who were able to have

[59:46] um their ovulation cycle restored.

[59:49] Um

[59:51] there was one study in

[59:53] women who

[59:55] were pregnant, and they found no

[59:57] negative effects of a 10-hour window on

[01:00:00] birth outcomes. So, things like how big

[01:00:02] is your infant, their Apgar score, which

[01:00:05] is like how well they're doing after

[01:00:07] delivering, and a bunch of other things.

[01:00:08] We don't have great data on this yet.

[01:00:10] >> Mhm.

[01:00:11] >> In rodents, some of those studies

[01:00:12] suggest negative effects on fertility. I

[01:00:14] doubt we'll see that in people. Cuz like

[01:00:16] the amount of the amount of fasting we

[01:00:18] do in rodents is actually quite extreme

[01:00:20] to the amount that we actually do in

[01:00:21] humans. So.

[01:00:22] >> window, right, is is is so you

[01:00:24] >> It's not that

[01:00:25] extreme.

[01:00:26] >> You'd like to think that you're asleep

[01:00:28] for seven of

[01:00:28] >> [laughter]

[01:00:28] >> the hours, you know? And so

[01:00:30] >> Ideally.

[01:00:31] >> Yeah.

[01:00:31] >> Yeah.

[01:00:32] >> Maybe not in practice. What about

[01:00:34] age-related differences? Do we do we

[01:00:36] know anything? Like if I'm

[01:00:38] should this apply in different ways to

[01:00:39] people at different times of their life?

[01:00:41] >> Yeah, we don't know, but there is um

[01:00:44] there are a small number of studies in

[01:00:45] older adults. One of the most amazing

[01:00:48] things um

[01:00:49] is two of those studies have found that

[01:00:51] time-restricted eating increases a

[01:00:53] 6-minute walk times.

[01:00:55] >> Love it.

[01:00:55] >> So, this is like how far you can walk in

[01:00:57] 6 minutes if you're elderly and have

[01:00:59] mobility issues. And to me, this is

[01:01:01] actually quite amazing, because this is

[01:01:03] not an exercise approach. This is like

[01:01:05] diet. Why should diet make you any

[01:01:07] better

[01:01:08] at your mobility? There should be

[01:01:09] absolutely none. Yeah, absolutely none.

[01:01:12] Um so, I find that amazing. And then

[01:01:13] about So, all of all the studies, so

[01:01:15] things that intermittent fasting doesn't

[01:01:17] seem to help with very much, cholesterol

[01:01:18] levels.

[01:01:20] Um unless you lose a lot of weight, then

[01:01:22] it'll lower your cholesterol levels. Um,

[01:01:25] and then heart rate, at least in the

[01:01:26] fasting state, but about half of studies

[01:01:28] that have measured heart rate while

[01:01:29] exercising find that it lowers heart

[01:01:31] rate while exercising. So, there's some

[01:01:33] sort of improvement there in

[01:01:35] cardiorespiratory fitness, and I've been

[01:01:36] asked, "What do you think's going on?" I

[01:01:38] have no idea.

[01:01:39] >> Mhm.

[01:01:39] >> Uh, which makes it interesting. Like,

[01:01:41] why does it? Yeah, exactly. Exactly.

[01:01:43] >> that note, are there any observed

[01:01:45] negatives, any downsides, uh, you know,

[01:01:48] not just things that don't improve, but

[01:01:49] things that get worse?

[01:01:52] >> Um,

[01:01:55] >> Like, lean lean tissue is the one that I

[01:01:57] I I talked

[01:01:58] >> Yeah, so that's the biggest one. Yeah.

[01:02:00] >> question. Muscle protein synthesis, but

[01:02:02] I I don't know if that's there's any

[01:02:04] good data for that.

[01:02:05] >> There's one study, and there's no effect

[01:02:06] on muscle protein synthesis with

[01:02:08] time-restricted eating.

[01:02:10] >> Or calories equated, I cal- macros and

[01:02:13] calories equated, I'd assume.

[01:02:15] >> I don't remember. I would have to go

[01:02:16] back and look, but there was no negative

[01:02:18] effect on muscle protein synthesis. I do

[01:02:20] still worry about lean mass for people

[01:02:22] who have done it a long time. Like, I

[01:02:24] think Peter Attia said he lost something

[01:02:26] like 10 lb of lean mass, but then when I

[01:02:28] heard what he was doing, I was like,

[01:02:29] "Oh, that's so extreme. I could have

[01:02:31] told you in advance you would have lost

[01:02:32] lean mass, cuz you're not just doing

[01:02:33] TRE, you're having multiple days of

[01:02:35] fasting multiple times a year." So, I

[01:02:37] definitely don't recommend that unless

[01:02:38] you have severe obesity and you need

[01:02:41] something like that. Um, negative

[01:02:43] effects, I think we do worry about

[01:02:45] pregnancy. I mean, I don't recommend it

[01:02:47] in pregnant women.

[01:02:49] Some intermittent fasting researchers

[01:02:51] don't feel as strongly as I do, but I

[01:02:53] wouldn't recommend it in pregnant or

[01:02:55] breastfeeding women. I would not

[01:02:57] recommend it in children,

[01:02:59] cuz one of the ways in which

[01:03:00] intermittent fasting has positive

[01:03:02] effects on the body is it slows the rate

[01:03:04] at which your cells grow and divide.

[01:03:06] >> Mhm.

[01:03:06] >> Or at least that's the best data we

[01:03:08] have. And so, I don't think it's

[01:03:09] appropriate for growing individuals. And

[01:03:12] there's a small fraction of men who are

[01:03:14] still growing in their early 20s,

[01:03:15] growing in height. And so, I wouldn't

[01:03:17] recommend it until your mid-20s. Um but

[01:03:19] again, I tend to err on the cautious

[01:03:21] side. And then for shift workers, we

[01:03:23] don't know what the optimal time of day

[01:03:24] is for them to eat cuz they have very

[01:03:26] different circadian rhythms. It's a

[01:03:27] tough gig. So, the best data we have is

[01:03:30] in people who do what's called simulated

[01:03:33] shift work, meaning that they're not

[01:03:34] shift workers themselves, but they adopt

[01:03:36] these schedules. And for them, it the

[01:03:38] data suggests it's better for them to

[01:03:39] eat when the sun is out. So, when it's

[01:03:41] daylight outside. But we don't know for

[01:03:42] certain cuz we don't yet have data in

[01:03:44] people who

[01:03:45] that those studies are underway, but we

[01:03:47] don't think we quite have a solid answer

[01:03:48] yet. So, there are not many negative

[01:03:50] things I know of in human humans. I

[01:03:52] think the biggest negative things are

[01:03:54] just the behavioral, which is like how

[01:03:55] does it impact your family life?

[01:03:58] Um but in terms of health, we don't have

[01:04:01] any

[01:04:02] strong signals like that yet.

[01:04:03] >> get into that like a bit of strategy.

[01:04:05] >> Yes. Okay.

[01:04:07] >> Because obviously as I've explained is

[01:04:09] I've I found find it quite difficult to

[01:04:10] do and I think people with, you know,

[01:04:12] very busy schedules, certainly with

[01:04:14] young children

[01:04:15] >> Yes.

[01:04:15] >> I mean, there's no chance getting a a

[01:04:17] kid to stick to an intermittent fasting

[01:04:18] schedule anyway, even if it was

[01:04:20] beneficial, I think. But um are there

[01:04:22] any good sort of practical tips and

[01:04:24] advice that you can give that can be

[01:04:26] like good takeaways to help people

[01:04:28] adhere to this? And And the reason I ask

[01:04:29] that is I think it sounds so compelling.

[01:04:31] The data is compelling. When we compare

[01:04:33] this to all of these other interventions

[01:04:35] that we're recommending for improving

[01:04:37] both

[01:04:38] quality of life, but likely length of

[01:04:40] life, it seems. We don't know for sure,

[01:04:42] but there's usually a correlation there.

[01:04:44] >> Yeah.

[01:04:44] >> Certainly quality of life. Um

[01:04:47] but so much of quality of life, I think

[01:04:49] for people is joy and, you know,

[01:04:52] community and and and a lot of that we

[01:04:54] experience

[01:04:56] around a dinner table, right? And I

[01:04:57] think um so, like any good tips or

[01:05:01] advice that you could give as sort of

[01:05:02] high-level strategies?

[01:05:04] >> Yeah, I can I can I'll give you several

[01:05:06] thoughts around this area. I don't have

[01:05:08] a magic bullet, too, um I'll say. So, we

[01:05:11] have found

[01:05:13] a small number of strategy strategies

[01:05:15] really help people kind of stick with

[01:05:17] this program. One we find a lot of our

[01:05:19] participants in our studies like to set

[01:05:20] alarms to remind themselves when to eat.

[01:05:23] And I think that becomes a kind of

[01:05:24] contract with yourself, keeping yourself

[01:05:27] accountable. And so, I think that's

[01:05:28] great. I don't set them myself, but I

[01:05:30] think if that works for you, amazing.

[01:05:32] The second thing that we have found is

[01:05:35] um

[01:05:37] for a lot of people their mood improves.

[01:05:40] And here's something where we actually

[01:05:41] have better data for intermittent

[01:05:43] fasting than calorie restriction. So,

[01:05:44] I'm involved in a clinical trial right

[01:05:46] now, we're wrapping up data analysis

[01:05:48] where we compared calorie restriction

[01:05:50] versus time restricted eating for

[01:05:52] slowing the aging process. Amazing

[01:05:54] study. We're measuring things like

[01:05:55] biological age, stem cell number,

[01:05:57] telomere length, mitochondrial function,

[01:05:59] nutrient sensing pathways.

[01:06:01] >> Wait, this is ongoing?

[01:06:02] >> Yes. Well, we we finished the study

[01:06:04] Well, we finished the study, we're

[01:06:05] analyzing the data, but I'm I'm still

[01:06:07] blinded, which means I don't know the

[01:06:09] results yet.

[01:06:09] >> It's like

[01:06:09] >> I don't know all the results. I know

[01:06:11] some of [clears throat] them. And we

[01:06:12] have some signals of some improvements

[01:06:14] in in in biological aging, which is

[01:06:16] exciting.

[01:06:17] Um

[01:06:18] but from that data, it seems that

[01:06:20] people's mood improves more with

[01:06:22] intermittent fasting um relative to

[01:06:24] calorie restriction. And that's despite

[01:06:26] the fact that people in our study people

[01:06:27] lost more weight with calorie

[01:06:28] restriction cuz we did a really

[01:06:30] intensive version of calorie restriction

[01:06:31] where they lose like a lot of weight.

[01:06:32] Think like big biggest losers style

[01:06:34] weight loss.

[01:06:35] >> Uh but mood was better. And I'll tell

[01:06:37] you in a lot of studies we have done,

[01:06:39] participants say their mood improves

[01:06:41] during

[01:06:41] >> What about energy levels? I think energy

[01:06:43] is the thing that You know, as soon as I

[01:06:45] hit my late 30s, 40s

[01:06:47] >> Yes.

[01:06:48] >> I felt like energy became a thing that

[01:06:51] I'd never been thinking about before and

[01:06:52] now I'm like every day it feels Is there

[01:06:55] any any data on that?

[01:06:57] >> Yeah, we we've also found that people

[01:06:58] have reported more energy levels and

[01:07:00] less fatigue, but we haven't

[01:07:02] Interestingly, we don't see any people

[01:07:04] don't report report an improvement in

[01:07:06] sleep quality.

[01:07:07] >> Mhm.

[01:07:08] >> So, we're like, where does that come

[01:07:09] come from, that boost in energy levels?

[01:07:12] Um one of our studies, we actually found

[01:07:14] that people were sleeping less when they

[01:07:16] did time-restricted eating. So, at first

[01:07:17] I was like I was kind of alarmed by

[01:07:18] that. I was like, oh no,

[01:07:20] is it disrupting their sleep? So, we

[01:07:22] looked at whether how hungry they were

[01:07:24] was, you know, correlating with um the

[01:07:26] degree to which they're they're they're

[01:07:28] sleeping and so forth. And when we

[01:07:30] looked closer at the data, it didn't

[01:07:31] look like people were staying up later

[01:07:33] or waking up earlier.

[01:07:35] Um

[01:07:36] >> Interesting you say that because

[01:07:37] anecdotally I think when I have been

[01:07:39] able to stick to it,

[01:07:40] >> Yes.

[01:07:40] >> I think I have slept slightly less, but

[01:07:42] I feel like that's because I felt like

[01:07:44] I've needed that sleep.

[01:07:45] >> That's correct. So, that's our leading

[01:07:46] We don't have proof of this yet, but my

[01:07:48] guess is it does something called

[01:07:50] consolidating sleep. So, it improves

[01:07:52] that. So, and it and again, this goes

[01:07:54] back to the idea of like intermittent

[01:07:55] fasting is kind of this period of rest

[01:07:57] and repair.

[01:07:57] >> Yeah.

[01:07:58] >> And so, if you have that longer period,

[01:07:59] maybe you don't need as much sleep. Or

[01:08:01] maybe the sleep you're getting is more

[01:08:02] regenerative.

[01:08:03] >> Yeah, more restorative and

[01:08:04] >> be

[01:08:05] >> alternates your sleep, so you know,

[01:08:07] it might improve the amount of deep

[01:08:08] sleep. Who knows?

[01:08:09] Um we will have data to answer this

[01:08:11] question. We put electrodes on some of

[01:08:12] our participants, so we'll be able to

[01:08:14] answer this hopefully in a year.

[01:08:15] >> for that one.

[01:08:16] >> Yeah. Awesome.

[01:08:17] >> that makes that makes a lot of sense in

[01:08:19] that if you're expending less or

[01:08:22] diverting less energy to digesting food,

[01:08:24] you can get on with that process of

[01:08:26] restoration that sleep brings you.

[01:08:28] >> Correct.

[01:08:28] >> Maybe.

[01:08:29] >> Yeah. Correct. Yeah, potentially.

[01:08:30] Potentially. I don't know. I mean, so

[01:08:32] again, this is another area like super

[01:08:34] interesting. I don't know for certain.

[01:08:36] Um so, other things that I think could

[01:08:37] help are meal planning.

[01:08:39] >> Mhm.

[01:08:39] >> And this is just I mean, even

[01:08:41] independent of intermittent fasting,

[01:08:42] such a great strategy. So, we find that

[01:08:45] people who prep their meals in advance

[01:08:47] are far more um able to stick with

[01:08:50] whatever diet they're on. And it can be

[01:08:52] like I don't even necessarily mean the

[01:08:54] the hardcore people who plan seven meals

[01:08:56] a week and weigh them all out. Like I'm

[01:08:57] not one of those type of people. I don't

[01:08:58] have time to be that one of people. But

[01:09:01] I'll make my food for the day in the

[01:09:02] morning. Yeah. I just, you know, do

[01:09:03] that. I have it ready. I'll have

[01:09:05] leftovers from like the night before.

[01:09:07] Like that's my lunch, you know? Like so

[01:09:09] I think meal prepping matters a lot. And

[01:09:11] then we've also found that just

[01:09:13] social support seems to matter.

[01:09:14] >> Sure.

[01:09:14] >> We have people in our studies that range

[01:09:17] from like their whole family's going to

[01:09:18] do it together, which matters a lot, to

[01:09:20] people who are like

[01:09:22] "My husband still wants me to cook and

[01:09:24] then he'll tease me."

[01:09:25] >> Yeah. Yeah.

[01:09:26] >> While I'm fasting. And I'm like, "Well,

[01:09:27] that's not cool." You know? So even if

[01:09:29] you you know, if you if you are even a

[01:09:31] partner of someone, you know, who who

[01:09:33] does this

[01:09:34] you can at least be neutral. Thank you,

[01:09:36] because you're helping that person.

[01:09:38] >> Because if you're having to prepare

[01:09:39] food, just being around food makes you

[01:09:41] feel hungry.

[01:09:42] >> And we have people who do great with

[01:09:43] that.

[01:09:43] >> Yeah.

[01:09:44] >> But I'll tell you, it feels a little bit

[01:09:45] like a punch in the gut if their partner

[01:09:46] or someone else is teasing them about it

[01:09:48] and saying, "Look at this great food I'm

[01:09:50] eating." right? So

[01:09:51] >> Courtney, I've heard you talk about this

[01:09:52] the concept of a metabolic kitchen. Can

[01:09:55] you can you explain how that is helping

[01:09:57] to move the science forward and and the

[01:09:59] implications of that?

[01:10:00] >> Yeah. So one of the things that my lab

[01:10:02] does that

[01:10:03] very few labs in the world can do is we

[01:10:05] use a metabolic kitchen to do these very

[01:10:07] precise assessments of people. So most

[01:10:09] of the studies on intermittent fasting

[01:10:10] go out, you tell people what to do, and

[01:10:12] they have to change their behaviors.

[01:10:14] >> Mhm.

[01:10:14] >> We have this kitchen where we can

[01:10:16] prepare all meals, and we can um

[01:10:19] and the beauty of that is

[01:10:20] then if we have people go do

[01:10:22] intermittent fasting, um we can make

[01:10:24] sure all the groups are eating the same

[01:10:26] amount of food. So if there's any

[01:10:28] differences between groups, it's not

[01:10:29] because one group had cornflakes for

[01:10:31] breakfast and another group like like

[01:10:33] skipped breakfast and then had like a

[01:10:35] turkey sandwich. So we can precisely

[01:10:38] match and control what people are

[01:10:39] eating. This also allows us, because we

[01:10:41] can prepare all meals and we give them

[01:10:43] to our participants, we can also um

[01:10:46] prevent them from gaining or losing

[01:10:48] weight. So a lot of my research has

[01:10:50] focused on are there benefits of

[01:10:52] intermittent fasting independent of

[01:10:53] whether you lose weight. And so in our

[01:10:56] studies, we were the first to show that

[01:10:57] intermittent fasting has benefits or at

[01:10:59] least some types. We don't know how

[01:11:01] broadly this generalizes

[01:11:03] can improve some aspects of your health

[01:11:04] even if you don't lose weight. So one of

[01:11:06] in one of our first clinical trials,

[01:11:08] we had men with pre-diabetes come in and

[01:11:12] they followed they ate within a 6-hour

[01:11:14] window or 12-hour window and they tried

[01:11:16] both schedules and on both schedules we

[01:11:18] fed them all their meals and the crazy

[01:11:20] thing is we actually watched them while

[01:11:21] they ate all their meals to make sure

[01:11:22] they're eating at the right time of the

[01:11:23] day.

[01:11:23] >> just thinking like prison.

[01:11:24] >> Yeah, it's a little bit like prison.

[01:11:26] They're paid. They're paid though. We do

[01:11:28] pay them well. But this is the second

[01:11:30] most rigorous type of study you can do

[01:11:32] and they're very hard to do. This first

[01:11:33] most rigorous which you almost never see

[01:11:35] done

[01:11:37] are living studies where you don't allow

[01:11:39] people to leave the lab. You know, it's

[01:11:40] very hard to find people who are willing

[01:11:41] to donate two two months of their lives

[01:11:43] for these studies. So we did in the next

[01:11:44] best thing. Which they don't live in but

[01:11:46] we feed them all their meals.

[01:11:48] >> two months?

[01:11:49] >> They can. In our studies we've Yeah,

[01:11:52] yeah, in our recent study they did it

[01:11:53] for two two months. It wasn't a living

[01:11:56] study but they had to eat only the food

[01:11:58] we served them. They had to video record

[01:12:00] themselves eating all the meals and we

[01:12:02] recorded the timestamps on every single

[01:12:04] video. So we knew that they were

[01:12:05] actually following schedule.

[01:12:07] >> How were you watching them?

[01:12:09] >> They record them.

[01:12:10] >> I I envisage it as like an interrogation

[01:12:12] room with a one-way mirror.

[01:12:14] >> They record themselves on a smartphone

[01:12:16] and then they upload it to a secure link

[01:12:19] that no one else can access and then we

[01:12:21] follow up with them. Yeah. Yeah. Yeah.

[01:12:22] Yeah. Yeah. Yeah. Yeah. Yeah. Yeah.

[01:12:23] Yeah. Yeah. Yeah. Yeah. Yeah. Yeah.

[01:12:23] Yeah. Yeah. Yeah. Yeah. Yeah. Yeah.

[01:12:24] Yeah. Yeah. Yeah.

[01:12:24] >> don't know for certain. Most of our

[01:12:26] participants but it's I'll tell you it's

[01:12:28] very hard. It's much harder for them to

[01:12:30] sneak the extra food.

[01:12:32] Because they're so full. Most of our

[01:12:34] participants say they're really full

[01:12:37] because the diets we feed them are

[01:12:39] generally a little bit higher fiber than

[01:12:40] they're than they're used to. Plus

[01:12:41] they're eating all their food in a short

[01:12:42] period of time. So we think the amount

[01:12:44] of cheating is low but it's far more

[01:12:46] rigorous and it's not perfect but it's

[01:12:48] far more rigorous than what anyone what

[01:12:50] everyone is doing.

[01:12:51] >> Well,

[01:12:51] >> I would imagine that given that they

[01:12:52] have volunteered to be part of the

[01:12:54] trial, they're not going to go and then

[01:12:55] cheat or certainly less of them are

[01:12:57] likely to.

[01:12:58] >> Yeah, yeah, yeah, much less likely. Much

[01:13:00] less likely. And the beauty of this too

[01:13:01] is when people are cheating, we usually

[01:13:03] can catch it cuz normally the way in

[01:13:05] which we'll see them cheating is they

[01:13:06] don't record videos of themselves. So,

[01:13:08] we will kick a number of people out of

[01:13:10] the study if they're not following not

[01:13:12] eating the foods or not eating at the

[01:13:14] right time. So, this allows us to catch

[01:13:16] and weed out the folks who either

[01:13:17] struggle or or not Usually, it's they're

[01:13:19] not seriously committed or they thought

[01:13:21] it would be an easier study.

[01:13:23] >> Yeah.

[01:13:23] >> Uh so to speak. So, my lab does about

[01:13:25] half of studies like this that are super

[01:13:27] rigorous and then the other half are

[01:13:28] like sort of classic studies where you

[01:13:30] go out and tell people to change their

[01:13:32] behaviors, but they report back to you.

[01:13:34] Um what they do.

[01:13:35] >> people not doing this?

[01:13:37] >> Expensive.

[01:13:38] >> It's just the cost.

[01:13:38] >> It's Yeah, it It costs and you need more

[01:13:40] training to do it. Um and you need the

[01:13:42] facilities to do it. And there are very

[01:13:44] few um institutions in the world that

[01:13:47] have these research kitchens. They're

[01:13:49] not hard to run, but you need a critical

[01:13:50] mass of scientists to do them and

[01:13:53] they're just expensive. So, I mean,

[01:13:55] before I came to Harvard, I mean, there

[01:13:57] probably only like a dozen places in the

[01:13:58] world that I could go at least in the US

[01:14:00] to do these types of studies. Not

[01:14:01] because it's hard, but but just that

[01:14:03] there's not the critical mass of

[01:14:04] researchers or they don't currently have

[01:14:06] a kitchen.

[01:14:06] >> This is a whole 'nother topic for

[01:14:08] discussion, but it feels like this this

[01:14:10] area of research is just so impactful

[01:14:13] for the nation's health that the funding

[01:14:15] situation we should have more than

[01:14:17] enough funding.

[01:14:18] >> So, actually, there was a heyday for

[01:14:20] this type of research. It's sometimes

[01:14:21] called like metabolic ward research, but

[01:14:24] some of the most profound insights we've

[01:14:25] got into energy or just metabolism in

[01:14:28] humans have come from these live-in or

[01:14:29] inpatient studies.

[01:14:31] I think it's about

[01:14:33] I might be wrong on the timeline, but it

[01:14:34] maybe uh two decades ago

[01:14:37] the NIH has several different

[01:14:39] institutes, but they have an institute

[01:14:41] um

[01:14:42] um that funded a lot of these programs.

[01:14:46] They funded what were called GCRCs, but

[01:14:48] allowed these very precise um studies to

[01:14:51] be done and then funding for that got

[01:14:54] cut and it killed a lot of research in

[01:14:56] this in this area. So, um

[01:14:59] what it took to for me to get these

[01:15:01] studies off the ground was actually

[01:15:02] really hard, not because

[01:15:05] the ex- like it was not rocket science,

[01:15:07] but

[01:15:08] the the will, the funding, or whatever

[01:15:10] [clears throat] to get off the study the

[01:15:11] ground was hard. So,

[01:15:12] >> low passive area.

[01:15:13] >> Yeah, I had to Yeah, a lot of of it

[01:15:15] variance to achieve the the goal. So,

[01:15:18] but these types of studies when they're

[01:15:19] done are phenomenal because you get to

[01:15:21] ask questions like, if someone can

[01:15:22] perfectly stick to a diet, what are the

[01:15:24] effects on health?

[01:15:25] So, if you for instance go out and ask

[01:15:27] people to follow Mediterranean diet,

[01:15:30] you know, they have to understand what

[01:15:31] that means, they have to have the money

[01:15:33] to buy the food, you know, and they may

[01:15:35] not understand what that fully means,

[01:15:37] but if we can go out and say, "Eat this

[01:15:39] food, we've already made it for you, and

[01:15:40] we'll usually even weigh out this food

[01:15:42] to the nearest gram." So, it's super

[01:15:43] precise. Um

[01:15:45] >> Even when you account for all of those

[01:15:46] things,

[01:15:47] >> Yes.

[01:15:47] >> um if they're not getting the food, then

[01:15:50] they can just under report. Like it just

[01:15:52] happens all the time.

[01:15:52] >> Exactly. So, these studies are actually

[01:15:54] very beautiful when you do them cuz you

[01:15:55] can usually see much bigger effects on

[01:15:57] health. And then you know, okay, this is

[01:15:59] the true effect on health cuz to me it

[01:16:01] answers the question, like is this an

[01:16:03] approach that's worth us studying? Like

[01:16:05] is there value to this? Cuz if you do a

[01:16:07] study like this and there's no benefit,

[01:16:09] well, there's just no benefit. Why are

[01:16:11] you wasting your time trying to find a

[01:16:12] way for people to do this?

[01:16:14] >> Can Can I ask you a personal question

[01:16:15] then? Given that you have successfully

[01:16:18] adhered to doing, you know, the earlier

[01:16:20] version of time restricted eating,

[01:16:23] have you What have been some strategies

[01:16:24] you've used for yourself with children

[01:16:27] after that period where you know you

[01:16:29] have to

[01:16:29] >> [clears throat]

[01:16:29] >> not eat then until you wake up the next

[01:16:31] day?

[01:16:31] >> Yeah, biggest secret is to make all my

[01:16:33] food in advance like that morning. I

[01:16:35] just

[01:16:36] put everything out. So, I'm a I'm a four

[01:16:38] meal a day person. Occasionally I I

[01:16:40] three, but I like four. There's no

[01:16:42] There's no scientific reason. It works

[01:16:43] well for me. Um

[01:16:45] And I think snacking is not great. And

[01:16:47] our generation, like the younger

[01:16:49] generation, tends to snack more and and

[01:16:51] eat later at night. Um so I just weigh

[01:16:53] them out. I eat at pretty much the same

[01:16:55] time every day. I get super hungry if I

[01:16:58] don't cuz I'm still so hyper adapted to

[01:17:00] that. So

[01:17:01] um I'll usually have my first meal

[01:17:03] starting between like 7:15 to 7:45. So

[01:17:07] roughly 7:30. I'll eat my next meal 2

[01:17:09] hours later. My next meal, you know,

[01:17:11] between 11:00 and noon. And then I just

[01:17:13] have one more meal.

[01:17:14] >> What time do you wake up in the morning?

[01:17:15] >> Uh 7:00.

[01:17:16] >> No, so you're eating fairly quickly

[01:17:18] after you wake up.

[01:17:18] >> Correct. Yeah, one of the other myths is

[01:17:20] that you can't eat right away when you

[01:17:21] wake up cuz a lot of people say you have

[01:17:23] elevated cortisol levels.

[01:17:25] That's true. Your cortisol levels are

[01:17:27] elevated, but there's a little bit of a

[01:17:29] time delay between when cortisol raises

[01:17:33] blood sugar levels. Like it's not

[01:17:34] immediate. And moreover, it's

[01:17:37] it's sort of outweighed by the fact that

[01:17:39] your body's better at secreting insulin

[01:17:41] in the morning and your what's called

[01:17:43] your insulin sensitivity, but that

[01:17:44] ability of that insulin hormone to do

[01:17:46] its job is also better in the day. So

[01:17:48] yes, cortisol's higher, but it's not the

[01:17:49] predominant factor that controls your

[01:17:52] blood sugar level. So if you're eating

[01:17:54] anytime after about 5:00 or 6:00 a.m. in

[01:17:56] the morning for most people. There are

[01:17:58] exceptions. So patients with type 2

[01:17:59] diabetes, they're an exception to the

[01:18:01] rule. People who do shift work, they're

[01:18:02] an exception to the rule. But for most

[01:18:03] people, you're already going to have

[01:18:04] good blood sugar control. If you can

[01:18:06] ideally also get outside

[01:18:08] uh before you eat um you know, I don't

[01:18:10] have my glasses here, but I actually

[01:18:12] have light therapy glasses that I wear

[01:18:13] in the morning that shine blue, green,

[01:18:15] white light

[01:18:15] >> as well. Yeah.

[01:18:16] >> You do? That's great. I use the Pegasi

[01:18:18] model. They're made in China.

[01:18:19] >> every Well, not now, but in the winter I

[01:18:21] was using them a lot.

[01:18:22] >> Yeah, so most mornings I'll wear the for

[01:18:24] those for an hour in the morning while

[01:18:25] I'm getting the kids ready for school.

[01:18:26] >> Do you think they work? I feel like they

[01:18:28] do.

[01:18:28] >> Well, we're testing them now. We're

[01:18:29] doing our clinical trials. Yeah, we're

[01:18:31] Our angle was to see if they improve

[01:18:33] blood sugar control, fat loss, circadian

[01:18:35] rhythm, sleep,

[01:18:37] um

[01:18:37] blood pressure, cardiovascular diseases

[01:18:39] >> like they certainly help me wake up

[01:18:41] quicker. And and I think if you live in

[01:18:43] New York,

[01:18:44] daylight is at a premium when you wake

[01:18:46] up in an apartment. And so yeah.

[01:18:48] >> Yeah, I'm quite taken with the data on

[01:18:50] sunlight, but there's not a lot of a lot

[01:18:52] of it. But, um, or certainly at least

[01:18:53] the data on circadian rhythms.

[01:18:55] Um, but the, um,

[01:18:58] the bright light will drop both

[01:19:00] melatonin and cortisol levels.

[01:19:03] And about it's roughly half of the

[01:19:04] population, it takes a while for their

[01:19:07] melatonin levels to drop in the morning.

[01:19:09] And melatonin will increase your blood

[01:19:11] sugar levels when it's elevated.

[01:19:12] >> Courtney,

[01:19:14] this is another question I'm planning

[01:19:16] for a friend. They asked me to ask you

[01:19:17] this.

[01:19:18] When you say, um,

[01:19:20] like breaking the fast,

[01:19:22] >> Yes.

[01:19:23] >> is that nil by mouth? Like nothing other

[01:19:25] than water? Like if if you were to have

[01:19:26] a black coffee first or electrolytes or

[01:19:29] some

[01:19:29] >> Yes.

[01:19:30] >> allowed or not?

[01:19:31] >> Um, we don't know for certain. Um, most

[01:19:35] of us researcher, so coffee we don't

[01:19:37] agree on as researchers whether it

[01:19:39] breaks the fast or not.

[01:19:41] Um, I've done studies both ways, full

[01:19:43] disclosure, where we've said coffee

[01:19:45] needs to be in window or you can have it

[01:19:47] anytime a day.

[01:19:48] A lot of studies will use a cutoff of

[01:19:50] like five calories. So, if something is

[01:19:52] less than five calories, we count it as

[01:19:54] fasting.

[01:19:54] >> probably be fine.

[01:19:55] >> Right, exactly. Black coffee would be

[01:19:57] fine, diet soda would be fine. I don't

[01:20:00] recommend diet soda, but I've worked in

[01:20:02] in uh geographic areas where diet soda

[01:20:05] is much more commonly consumed.

[01:20:06] >> Yeah, than water.

[01:20:07] >> Or in populations, cuz we're often

[01:20:09] working with people who are sick and

[01:20:10] want to improve their health or have

[01:20:11] some sort of condition where they want

[01:20:13] to improve their health.

[01:20:14] Um, squeeze of lemon, fine. We say

[01:20:17] chewing gum's fine.

[01:20:18] Um,

[01:20:20] the reason why coffee has been

[01:20:21] controversial is we know it affects

[01:20:23] some, I'm just going to say metabolic

[01:20:25] pathways. And so the question is like

[01:20:27] how much

[01:20:28] does does does does this really count?

[01:20:31] There are some studies There are some

[01:20:33] people who say that having a high-fat

[01:20:36] meal shouldn't really count as breaking

[01:20:38] the fast, but I don't agree with that.

[01:20:40] Um

[01:20:42] >> Wait, who's saying this? That sounds

[01:20:43] outrageous to

[01:20:45] >> I've seen a couple studies in the

[01:20:46] literature where they try to extend the

[01:20:48] fast by people giving people a high-fat

[01:20:50] energy bar.

[01:20:51] >> No way.

[01:20:51] >> I don't buy it, though.

[01:20:52] >> a pie. That's a made-up rule, for sure.

[01:20:54] >> Well, so So, a lot of people think that

[01:20:56] a lot of the mechanisms of intermittent

[01:20:57] fasting are the same mechanisms for

[01:21:01] low-carb diets, meaning the ways in

[01:21:02] which these things work are the same.

[01:21:04] >> Yeah.

[01:21:04] >> But, there are also small number studies

[01:21:06] that show right Yes, there's some

[01:21:07] overlap, but there are a lot of

[01:21:08] differences, too. It's not the same.

[01:21:10] >> Mhm.

[01:21:11] >> the same.

[01:21:12] >> It's nuanced.

[01:21:13] >> It's nuanced, yeah.

[01:21:14] >> I think that the most exciting thing is

[01:21:15] that

[01:21:17] as a as a topic as a whole, it it just

[01:21:19] seems incredibly beneficial for the

[01:21:22] amount of lift and energy that it takes.

[01:21:24] >> yes, there was a nice survey done last

[01:21:26] year. Um

[01:21:28] Most people don't know this, but

[01:21:29] intermittent fasting now is about as

[01:21:30] popular as GLP-1s, but you see more

[01:21:33] press on on GLP-1s. So, it's the third

[01:21:35] most commonly practiced diet diet in the

[01:21:38] US among people who practice or

[01:21:40] subscribe to particular dietary

[01:21:42] uh pattern. So, it's kind of exploded in

[01:21:45] popularity. Um so, it's about 13% of the

[01:21:47] US population practices intermittent

[01:21:49] >> As it should, you know, I'm I'm

[01:21:52] I've said this before, I'm worried about

[01:21:53] the long-term effect on certainly on

[01:21:55] body composition, like lean tissue mass

[01:21:58] and bone density for for this very rapid

[01:22:00] weight loss. I think we're starting to

[01:22:02] see that data on bone now, which we

[01:22:04] hadn't in the past, and I

[01:22:06] I think that's worrying, especially in

[01:22:07] an aging population.

[01:22:08] >> Yeah. So, um I'm good friends with the

[01:22:11] scientist who did the longest study of

[01:22:13] calorie restriction in humans, and the

[01:22:15] goal there was to slow the aging

[01:22:16] process.

[01:22:17] The interesting thing they found is

[01:22:19] around 1 to 1 and 1/2 years after

[01:22:22] cutting their calories by about 25% body

[01:22:24] their body weight started plateau. So,

[01:22:26] they started to either, you know,

[01:22:27] maintain their weight or start to

[01:22:29] rebound a little bit.

[01:22:30] But, they continued to lose bone.

[01:22:32] >> Yeah.

[01:22:33] >> Afterwards. And that scares me, right?

[01:22:34] Because technically they're no longer

[01:22:35] losing weight and they're still losing

[01:22:37] bone.

[01:22:37] >> Yeah.

[01:22:38] >> So, I worry about that. I worry about

[01:22:39] loss of lean tissue. Um and that's going

[01:22:42] to set you up to to for extra fat to be

[01:22:45] stored in some of your organs, which we

[01:22:46] know leads to a lot of these metabolic

[01:22:48] diseases.

[01:22:49] >> just becomes incredibly difficult to get

[01:22:51] that back. You know, bone almost

[01:22:52] impossible.

[01:22:53] >> Yeah. And I'm not opposed to GLP-1s. I'm

[01:22:56] sort of a like, let's do lifestyle

[01:22:57] first. If all else fails, and you have,

[01:23:00] you know, a severe obesity or some other

[01:23:02] condition, like these these are

[01:23:04] life-saving drugs.

[01:23:04] >> Yeah.

[01:23:05] >> So, I don't want to be misinterpreted,

[01:23:07] but I'm generally a like, lifestyle

[01:23:08] first, fancy stuff second person.

[01:23:10] >> if it's for aesthetic or, you know,

[01:23:13] overall feeling of well-being and not

[01:23:15] like

[01:23:16] a dramatic need for for weight loss.

[01:23:18] That is a whole 'nother episode there,

[01:23:20] I'm sure. Okay, I'm mindful of your time

[01:23:22] here and so I'm going to move on to some

[01:23:24] quick fire questions.

[01:23:25] >> Sure. Okay.

[01:23:25] >> Okay.

[01:23:26] >> Great.

[01:23:26] >> And the the only rule here is that you

[01:23:28] can't spend more than 30 seconds

[01:23:30] answering each.

[01:23:31] >> Okay.

[01:23:31] >> Okay.

[01:23:32] >> Good deal.

[01:23:32] >> What would you say is the most overhyped

[01:23:35] longevity trend

[01:23:37] right now?

[01:23:39] >> That is such a hard question.

[01:23:41] >> You can have more than 30 seconds for

[01:23:42] this then cuz it's important.

[01:23:44] >> There's so many. I don't know if there's

[01:23:46] a standout.

[01:23:48] >> Well, then you can say more than one.

[01:23:50] >> what I would say is a a lack of focus on

[01:23:52] the fundamentals.

[01:23:53] >> Mhm.

[01:23:55] >> Which I know you we were talking about

[01:23:56] earlier, but I generally I'm like a John

[01:23:58] Wooden kind of people. For people who

[01:24:00] don't know, famous basketball coach and

[01:24:02] his one of the most winning basketball

[01:24:03] coaches of all times. And he was like,

[01:24:05] players come in they want to focus on

[01:24:06] the layups.

[01:24:07] >> Mhm.

[01:24:08] >> But, it's all about the free throws that

[01:24:09] you shoot like a gazillion times a day

[01:24:11] and like the fundamentals. So, I'm a

[01:24:13] fundamental person. Like, don't look at

[01:24:15] these trends like red light red light

[01:24:17] therapy, sauna, etc. until you get your

[01:24:19] own on in gear. So, I'll give you an

[01:24:20] example. So,

[01:24:22] in the last 6 years I've given birth to

[01:24:23] two children. I've lost both my parents.

[01:24:25] I'm still grieving from the loss of my

[01:24:27] mom.

[01:24:28] Um I've been bedridden from uh

[01:24:31] uh an epidural gone wrong. Um lost a lot

[01:24:33] of muscle mass, which I've rebuilt. Um

[01:24:35] and I had long COVID or the equivalent.

[01:24:38] And I haven't slept enough.

[01:24:40] But, I'm getting my life back in gear.

[01:24:42] So, I just started sleeping um the last

[01:24:45] week. And my process is going to be So,

[01:24:48] I've always been really good with diet.

[01:24:49] That that comes easily to me. So, that's

[01:24:51] always been in gear regardless of how

[01:24:53] chaotic life is. But, my goals for the

[01:24:55] you know, for the first time sleep

[01:24:57] number one. I'm going to get back to

[01:24:58] five sleep cycles a night, which is my

[01:25:00] target. And then get exercise back in

[01:25:02] gear. And I'm going to do all of that

[01:25:04] and you know, create a solid foundation

[01:25:06] before I think about any fancy

[01:25:09] tools and all this stuff.

[01:25:10] >> I think you've effectively answered my

[01:25:12] next question, which is what is the most

[01:25:14] underhyped

[01:25:15] longevity trend. Anything to add to

[01:25:17] that?

[01:25:18] >> I mean, I think I would say sleep.

[01:25:20] >> Mhm.

[01:25:21] >> I think people tend to understand

[01:25:22] exercise and diet are important, but I

[01:25:24] would say sleep.

[01:25:26] Um and if I were to put a second one,

[01:25:28] I'd put maybe purpose or mental health.

[01:25:30] >> Mhm.

[01:25:31] Love that.

[01:25:32] >> And I think it's not just mental health,

[01:25:34] because you can feel happy, but you can

[01:25:35] be empty if you don't know like why

[01:25:37] you're here, what you're doing, or you

[01:25:38] have like some mission or some purpose

[01:25:40] greater than yourself. And it can be

[01:25:41] small, but still meaningful to you.

[01:25:44] >> And I think it's actually

[01:25:45] >> your life has meaning.

[01:25:46] >> Yeah, and I think it's actually easier

[01:25:47] to cope with the periods of unhappiness.

[01:25:50] >> Yeah, absolutely.

[01:25:50] >> purpose as well.

[01:25:52] >> Yeah.

[01:25:52] >> Okay.

[01:25:53] >> But, sleep. I think too many people cut

[01:25:54] their sleep short. And my guess is

[01:25:57] you know, actually one of the things I

[01:25:58] used to like to say to some of my

[01:26:00] students in the lab is what do you think

[01:26:01] is the fastest way towards elevating

[01:26:03] your blood sugar levels? Big Mac,

[01:26:05] being sedentary,

[01:26:07] or uh losing sleep? And the answer is

[01:26:09] losing sleep. With sleep restriction 4

[01:26:12] to 6 hours, you can worsen insulin

[01:26:13] sensitivity by about 33% overnight.

[01:26:16] >> How much you averaging a night right

[01:26:17] now?

[01:26:18] >> Um last night I got about 7 1/2 hours of

[01:26:21] sleep, but I've been more I've been

[01:26:23] closer to 7, but my sweet spot is 7 1/2

[01:26:26] to 8, so that's my first goal for

[01:26:27] myself.

[01:26:28] >> track your Do you wear a wearable?

[01:26:30] >> I do, but I'm not a huge tracker.

[01:26:31] >> No, me neither.

[01:26:32] >> Because I'm more of a like let's focus

[01:26:34] on the fundamentals. So I I actually am

[01:26:36] using the tracker right now to measure

[01:26:38] my sleep time. Um and I'll measure my

[01:26:40] steps. With that said, I don't really do

[01:26:42] fancy stuff. Occasionally I'll measure

[01:26:43] my heart rate if I want to be in a

[01:26:45] certain zone.

[01:26:46] >> I think capturing that data is

[01:26:47] incredibly valuable. More data is

[01:26:49] better, but I don't think you need to do

[01:26:51] it continuously, especially when you

[01:26:53] start to get some intuition about what

[01:26:55] is right for you and the longer you you

[01:26:56] do it for. So I like to do it like every

[01:26:58] quarter I'll do a couple of weeks of

[01:27:00] tracking everything and then I can

[01:27:01] observe that.

[01:27:02] >> I think intensive tracking for short

[01:27:04] period of times is fantastic. I actually

[01:27:06] do So let me make an exception to the

[01:27:08] rule. I said So I think intensive

[01:27:10] tracking for short period of time is

[01:27:11] really helpful. We see it a lot actually

[01:27:13] for nutrition studies cuz sometimes

[01:27:14] they'll be like, "Oh, I think I know how

[01:27:16] much I'm eating." And they're like

[01:27:17] dollop of peanut butter here, but it's

[01:27:18] like double. It's two ta- tablespoons,

[01:27:20] not one or something like that. So I

[01:27:22] think intense periods of tracking to see

[01:27:24] where you are are great, but long-term

[01:27:26] I'm more of a minimalist.

[01:27:28] >> What does it What does a normal day of

[01:27:30] eating look like for you? Not the

[01:27:31] timing, but the the the the types of

[01:27:34] food.

[01:27:35] >> so this is where I have kind of like a

[01:27:36] rough formula for saying I think it

[01:27:38] keeps it easy, but it still gives me

[01:27:40] flexibility. So uh morning is a

[01:27:42] smoothie. It's a giant fruit smoothie

[01:27:44] with flax seeds, bananas and orange,

[01:27:47] berries, a little bit of almond milk,

[01:27:50] and a little bit of protein powder.

[01:27:52] >> Wait, you put the orange in with almond

[01:27:54] milk?

[01:27:54] >> I do.

[01:27:55] >> It's criminal.

[01:27:56] >> [laughter]

[01:27:57] >> A little bit of dates, yeah.

[01:27:58] >> Okay.

[01:27:59] >> Uh so this is my sweet spot. Um it works

[01:28:01] well for me. I just rotate the berries

[01:28:02] every day, so keep it interesting. Um

[01:28:05] second meal of the day is a lot of

[01:28:07] fruit, dried fruit, fresh fruit, um

[01:28:11] nuts. I'll do a handful of nuts. I'm

[01:28:12] really quite convinced by the data on

[01:28:15] nuts.

[01:28:16] >> Which is kind of ironic cuz I was

[01:28:17] recently part of nutrition class and a

[01:28:19] lot of people still fear fat.

[01:28:21] >> Mhm.

[01:28:21] >> And I believe there good carbs and bad

[01:28:23] carbs and good fats and bad fats.

[01:28:25] >> Yeah.

[01:28:25] >> So, um

[01:28:26] >> We had Dariush Mozaffarian from the

[01:28:28] Friedman School of Nutrition in Boston

[01:28:29] last week.

[01:28:30] >> Um lunch for me is always a meal of

[01:28:32] beans, mostly beans and vegetables. And

[01:28:34] then I'll do a third of a pound of

[01:28:35] steamed greens. And then my last meal of

[01:28:37] the day is a fruit smoothie with um 2/3

[01:28:40] of a pound of greens.

[01:28:41] >> What's your guilty pleasure?

[01:28:43] >> Chocolate, dark chocolate. I'll often

[01:28:44] have a square or two a day. So, that's

[01:28:46] my treat, you know.

[01:28:47] >> Do you ever drink alcohol?

[01:28:49] >> I don't. Uh very rarely. Um

[01:28:52] largely it's for reasons of taste, but

[01:28:54] yeah.

[01:28:55] >> It's going out of fashion anyway.

[01:28:57] >> it is, surprisingly.

[01:28:58] >> Yeah.

[01:28:58] >> But, yeah.

[01:28:59] >> What do you think is one trend we'll

[01:29:00] look back on in

[01:29:03] 10 years time as in I can't believe we

[01:29:04] used to believe that's true or I can't

[01:29:06] believe we used to do that.

[01:29:09] >> Gosh, I feel like we go through all

[01:29:10] these trends in nutrition about, you

[01:29:12] know, fat is bad, fat is good, protein

[01:29:15] is bad, protein is good. And I think

[01:29:17] we'll just go more towards focus My hope

[01:29:19] is whole foods.

[01:29:21] >> Yeah.

[01:29:22] >> foods.

[01:29:23] Um there are other things, but they're

[01:29:24] more in the like

[01:29:25] >> well. I think this is we're making

[01:29:27] progress.

[01:29:27] >> Yeah, I think so, too. Um and then I

[01:29:30] think we focus a lot on aesthetics

[01:29:33] and trying to slow the aging process

[01:29:35] from aesthetics. So, I wonder if certain

[01:29:38] aesthetic approaches will be like, why

[01:29:39] did we ever do that?

[01:29:40] >> Why did we care about that? Right, yeah.

[01:29:43] >> What is one thing that

[01:29:44] >> Not not that I don't think people will

[01:29:45] care about aesthetics, but they'll

[01:29:46] probably tend to use more natural

[01:29:47] approaches. So, I'll give you an

[01:29:48] example. I I've not had any treatments

[01:29:50] done myself, but like

[01:29:53] uh we inject our face or society, a lot

[01:29:56] of people inject their faces with these

[01:29:58] artificial fillers. And I think in the

[01:30:00] long term people will go with a more

[01:30:01] natural approaches like fat fat grafting

[01:30:03] or I I forget the term for it, but you

[01:30:05] know, implanting fat rather than these

[01:30:07] artificial fillers, things

[01:30:08] >> like that.

[01:30:09] >> There is a time for that. Oh, I don't

[01:30:10] know it.

[01:30:10] >> I know, and I should know it, but I

[01:30:11] don't I don't remember it. Yeah.

[01:30:13] >> Okay, I'm going to find that out in the

[01:30:14] skin care world.

[01:30:14] >> we'll be going for more natural

[01:30:15] approaches like maybe micro needling

[01:30:17] with PRP or some things like that or

[01:30:19] using light and less of these

[01:30:21] >> Yeah.

[01:30:21] >> um more artificial Yeah.

[01:30:23] >> What what is one thing that

[01:30:26] you wish you'd known 20 years ago

[01:30:29] that you would tell your

[01:30:31] self back then?

[01:30:32] >> Oh my goodness. In regards to

[01:30:35] >> health

[01:30:36] >> or broadly speaking life?

[01:30:38] >> either.

[01:30:41] >> Oh gosh, I don't know. That is a tough

[01:30:44] >> not really quick fire, are they? Like my

[01:30:46] questions. [laughter]

[01:30:47] >> That's okay. You get to see my you get

[01:30:49] to see my

[01:30:50] candid responses.

[01:30:52] I don't know. I think my weakness from a

[01:30:54] health perspective is stress.

[01:30:56] Some of that's time management. I feel

[01:30:58] like I have great skills, but I need

[01:30:59] even even better skills than I have.

[01:31:02] Um with everything on my plate, so I

[01:31:03] think

[01:31:04] maybe this is not quite a perfect

[01:31:06] answer, but I think figuring out how to

[01:31:08] deal with stress, what that looks like,

[01:31:10] work-life balance.

[01:31:11] I work intensely hard. Carving out time

[01:31:14] for myself is hard.

[01:31:15] >> Yeah.

[01:31:16] >> I don't have an answer, but that's a

[01:31:17] weak area of mine.

[01:31:19] >> Yeah.

[01:31:20] Okay, if money were no object

[01:31:23] you have all the resources in the world

[01:31:25] >> Yes.

[01:31:25] >> all the funding, all the backing in the

[01:31:27] world, what unanswered question within

[01:31:29] your domain would you like to

[01:31:31] >> Yeah.

[01:31:31] >> answer? Like if we could get any amount

[01:31:33] of funding to answer a question

[01:31:35] >> Um

[01:31:35] >> Yeah.

[01:31:35] >> or move the science forward, what would

[01:31:36] that be?

[01:31:37] >> Yeah, two. And I know exactly what they

[01:31:39] are and I've been thinking about them

[01:31:40] for years. Okay.

[01:31:41] Um the first one's in the realm of

[01:31:42] intermittent fasting, the second's in

[01:31:44] the realm of diet quality. For

[01:31:45] intermittent fasting

[01:31:47] I want to bring people in the lab, test

[01:31:51] uh intermittent fasting by eating early

[01:31:52] in the day or time-restricted eating by

[01:31:54] eating early in the day, late in the day

[01:31:56] and do really deep

[01:31:58] we've been calling it phenotyping.

[01:32:00] >> Yeah.

[01:32:00] >> But I want to know

[01:32:03] Um I want to also use something called

[01:32:05] stable isotope tracers, which is a fancy

[01:32:08] way of like tagging molecules so we can

[01:32:10] follow them in the body.

[01:32:11] >> Mhm.

[01:32:11] >> So I want to do is line up what's going

[01:32:13] on with metabolism, like where people

[01:32:15] are in their sort of fat burning versus

[01:32:17] glycogen store burning process

[01:32:20] as a function of the number of hours

[01:32:22] they've been fasting.

[01:32:23] And then also overlay

[01:32:26] that with measuring

[01:32:28] the hallmarks of aging or major

[01:32:29] biomarkers of aging and measuring them

[01:32:31] at least once an hour over the course of

[01:32:33] the day so we can kind of see not only

[01:32:36] how the degree of fast that both the

[01:32:38] time of day you're eating and the amount

[01:32:39] of fasting you do you do affects these

[01:32:41] biomarkers, but also understand like how

[01:32:44] much of this varies individual by

[01:32:46] individual like you know, if you have

[01:32:48] excess fat to lose, maybe you need to

[01:32:50] last fast longer

[01:32:52] >> Yeah.

[01:32:53] >> to these sort of like therapeutic

[01:32:54] rejuvenating rejuvenating range. So

[01:32:57] these are very hard and very expensive

[01:32:58] studies to do. So for instance, I had,

[01:33:01] you know, a two and a half million

[01:33:02] dollar grant from the NIH and we did a

[01:33:05] similar study to this called our meal

[01:33:07] timing study where we brought people in

[01:33:08] and we couldn't measure all these things

[01:33:09] cuz it's so expensive, but just to bring

[01:33:10] people in and to measure

[01:33:12] primarily just a small number of things

[01:33:13] like glucose, insulin, and blood

[01:33:16] pressure. I mean, we could only we ran

[01:33:18] less than 100 people and we couldn't

[01:33:19] even do any of these assessments. I

[01:33:20] mean, so they're so expensive. So that

[01:33:22] would be the first dream study. And then

[01:33:23] we can also look at all these

[01:33:24] inter-individual differences, but I

[01:33:26] think a study like that could blow open

[01:33:29] multiple fields.

[01:33:30] >> Yeah.

[01:33:30] >> been thinking about how to get that

[01:33:31] funded for years cuz I can't fund that

[01:33:33] under a traditional NIH mechanism. And

[01:33:35] the second study in diet quality is I'm

[01:33:37] really interested in food as medicine.

[01:33:38] Like can you take someone with a chronic

[01:33:39] disease

[01:33:41] you know, about 30 years ago we used to

[01:33:43] think type 2 diabetes was not

[01:33:44] reversible. Um we now have data from

[01:33:47] something called the direct trial. We're

[01:33:48] putting people on a very low calorie

[01:33:50] diet so less less than 800 calories for

[01:33:52] about 12 to 20 weeks.

[01:33:54] Um puts people in remission from type 2

[01:33:57] diabetes. About 46% of patients go into

[01:33:59] remission. I'd love to push that higher

[01:34:02] and test different diets for diabetes

[01:34:03] remission and see if we can get it just

[01:34:05] by improving diet quality,

[01:34:06] >> Yeah.

[01:34:06] >> not by cutting calories that

[01:34:08] dramatically. Um so, I'd love to do a

[01:34:10] study to see if we can reverse type 2

[01:34:12] diabetes testing different diets for

[01:34:13] that, which would also be an expensive

[01:34:14] study. But, those are my two dream

[01:34:16] studies. Those are my two dream studies.

[01:34:18] >> Okay.

[01:34:18] >> If I could If I could only do two other

[01:34:19] studies for most of my life, those would

[01:34:21] probably be it.

[01:34:23] And I would measure in the first study

[01:34:26] I'd measure biological age. Maybe

[01:34:27] there's one other study I have that

[01:34:29] would compete with that, but that gives

[01:34:30] you a sense.

[01:34:31] Yeah.

[01:34:32] >> I think that's where there are companies

[01:34:33] that can sort of step in and that be the

[01:34:35] work.

[01:34:36] >> of some parts of this.

[01:34:37] >> Privately funded in some parts and yeah.

[01:34:39] Okay, two more questions and then and

[01:34:42] then you're free.

[01:34:43] >> Okay.

[01:34:44] >> First one is

[01:34:46] what makes you most optimistic about

[01:34:48] this field at the moment? You know, what

[01:34:50] what in the space and it can be in a

[01:34:51] different domain of science? Like, where

[01:34:53] are you where are you feeling positive?

[01:34:56] >> Um I think the number of people who are

[01:34:58] interested in intermittent fasting and

[01:35:00] nutrition has dramatically increased.

[01:35:03] And I think now the current

[01:35:05] administration is trying to get

[01:35:06] nutrition taught more in medical

[01:35:08] schools.

[01:35:09] >> Mhm.

[01:35:10] >> So, I think we're I think the interest

[01:35:12] is there. We just need the funding to

[01:35:14] make things happen.

[01:35:15] >> Yeah.

[01:35:15] >> So, um

[01:35:17] for instance, less than 5% of the NIH

[01:35:19] budget funds nutrition even though it's

[01:35:21] a leading cause of death and disease.

[01:35:22] And so, I I I think I think the will to

[01:35:26] do the work is there now. And

[01:35:27] interestingly, I think

[01:35:29] all of the popularity in social media

[01:35:31] has been good for scientists in a sense.

[01:35:34] I think people tend to think of it as

[01:35:35] all negative. And yeah, there are not

[01:35:37] negative elements, but I think there are

[01:35:38] a lot of positive elements. I think we

[01:35:40] just need the pathways to get there. I

[01:35:42] don't want to say quite that we need a

[01:35:44] moonshot in nutrition cuz it's not one

[01:35:46] single effort, but I think we need

[01:35:49] the government, private individuals to

[01:35:51] help us get there cuz the will is there.

[01:35:54] It's just the pathways or the funding is

[01:35:56] is not quite there.

[01:35:58] >> Okay, last one.

[01:36:00] >> Yes.

[01:36:00] >> This is tough.

[01:36:00] >> Okay.

[01:36:02] >> If the listeners of this podcast

[01:36:05] only tuned in right now,

[01:36:06] >> Okay.

[01:36:08] Yeah.

[01:36:08] >> what would be the one takeaway that you

[01:36:10] would give them?

[01:36:12] >> I would say that our best evidence in

[01:36:15] people suggests that eating um having a

[01:36:17] longer daily fasting duration, ideally

[01:36:20] if you can do 16 hours a day, if not 14,

[01:36:24] and or eating early in the day looks

[01:36:26] like it improves their health, and if

[01:36:27] they can come up with some sort of

[01:36:30] daily schedule they can follow 5 days a

[01:36:32] week that incorporates this principle,

[01:36:34] they'll probably see some health

[01:36:35] improvements.

[01:36:37] >> Courtney,

[01:36:39] thank you so much. That [music] was a

[01:36:40] privilege and a pleasure.

[01:36:42] >> You're welcome. Thanks for having me.

[01:36:43] >> for episode two.

[01:36:44] >> Okay. Great.