Fasting & the Best Times to Eat | Dr. Casey Means & Dr. Andrew Huberman

00:00:00.000 | The way I conceptualize the idea of fasting, obviously this is one where we need more words,

00:00:06.720 | right?

00:00:07.720 | Because the word fasting is so limited, there's so many different parts of this, but…

00:00:11.640 | Skipping breakfast for me would be that, or skipping dinner.

00:00:14.440 | Right.

00:00:15.440 | Sometimes I'll skip dinner, sometimes I'll skip breakfast.

00:00:18.000 | Right.

00:00:19.000 | I think that some of the most interesting data that I've seen has been about if we

00:00:23.840 | reasonably compress our eating into daytime hours during the part of the diurnal cycle

00:00:31.000 | when we are supposed to be eating.

00:00:33.160 | So essentially matching our chronobiology with our behavior, which, you know, we are

00:00:39.080 | diurnal organisms, so we kind of need to respect that.

00:00:42.080 | Like when we do that and we compress it in a moderate way, our metabolic health is better.

00:00:47.840 | And so some of the studies that have looked at this, one that was interesting was, and

00:00:52.720 | I think very hopeful for people, is that if you take all the food, all the calories that

00:00:57.560 | you're going to eat, and eat them in a 6-hour window versus a 12-hour window, totally same

00:01:05.120 | amount of calories, exact same food.

00:01:06.800 | This is a controlled experiment.

00:01:09.620 | People who eat the same amount of calories in a 6-hour period are going to have much

00:01:14.000 | lower, statistically significantly lower, glucose, 24-hour glucose and insulin levels

00:01:19.120 | compared to people who just space it out over the course of a 12-hour period.

00:01:23.640 | And it makes sense because if you're spacing that food out over the course of 12 hours,

00:01:29.560 | that is a different biochemical milieu in your body throughout the day.

00:01:33.360 | It's kind of similar to the walking.

00:01:34.600 | You know, it's like you are then stimulating insulin several more times.

00:01:39.760 | You are exposing the bloodstream to insulin and glucose just more throughout the day.

00:01:46.920 | And giving the bloodstream less of an opportunity to just sort of be clear from that glucose

00:01:52.160 | and that insulin.

00:01:53.380 | And so compressing our eating window seems to be helpful for metabolic health.

00:01:58.760 | And it's a bang for your buck, right?

00:02:00.440 | Like you can eat the same amount of food.

00:02:01.800 | You just have to eat in a shorter period of time.

00:02:03.480 | So for people who want to eat, you know, a lot, maybe just consider compressing it into

00:02:08.520 | daytime hours, 6- to 8-hour window.

00:02:11.160 | Yeah.

00:02:12.160 | For me, 6 is tough.

00:02:13.160 | 6 is tough, yeah.

00:02:14.160 | The one meal per day thing is tough.

00:02:15.160 | I have friends like Lex Freedman that do the one meal per day thing.

00:02:17.480 | I end up eating so much food at that meal that I experience a lot of kind of like mechanical

00:02:21.800 | distress as typically later in the day.

00:02:24.280 | I think an 8- to 10-hour window has worked well for me most days.

00:02:29.380 | I know as soon as we talk about intermittent fasting, which is what, or time-restricted

00:02:33.320 | feeding, same thing, which is what we're talking about right now, I'm sure somebody is going

00:02:37.480 | to call up the, there's been a study that's been circulating about a massive increase

00:02:44.440 | in cardiovascular risk in people doing intermittent fasting and particularly the 6-hour feeding

00:02:49.000 | window.

00:02:50.000 | I just want to point out.

00:02:51.000 | Worst study.

00:02:52.000 | As far as I know, I could be wrong, but as far as I know, that study is still in abstract

00:02:56.440 | form.

00:02:57.440 | It's not yet peer-reviewed.

00:02:58.440 | Yeah.

00:02:59.440 | It's like the fact that studies that haven't been peer-reviewed aren't even close to being

00:03:04.480 | peer-reviewed are being like put out there as new stories is really problematic because

00:03:10.800 | I can tell you as somebody who sat on the editorial boards of many journals for many

00:03:14.480 | years, I still sit on a few, reviewed countless papers, I've submitted and had to deal with

00:03:19.240 | reviews on countless papers, the fact of the matter is like until the reviews are done,

00:03:24.640 | the revisions are made, like that paper may never see the light of day and it may end

00:03:28.720 | up in a journal that you, is barely worthy of a placemat.

00:03:33.020 | It might end up in a high-tier, high-quality journal, but it might not.

00:03:35.800 | So just because there was "a study done" means very little, but it means especially

00:03:40.640 | little, maybe nothing until it's peer-reviewed.

00:03:42.680 | Absolutely.

00:03:43.680 | And the methods were very poor in that study.

00:03:46.080 | It was a recall-based study, I think, for two days of recall of people's diets, which

00:03:52.240 | is notoriously very bad in terms of accuracy.

00:03:55.200 | So yeah, and I think I'm not in any way suggesting that a six-hour window is the optimal window.

00:03:59.920 | I'm just sharing the data that suggests that compressing the window seems to have a favorable

00:04:06.840 | effect, and I certainly don't do six hours, but I think when you look at what the average

00:04:11.560 | American is doing, which is the average American has 11 eating events per day and 50% of Americans

00:04:20.400 | eat over a 15-hour window per day.

00:04:24.040 | I can recall those because I remember when I was writing the book, I was like, "That's

00:04:28.120 | a long time, 15 hours and 11 events," and every time you're doing that, you're going

00:04:33.920 | to be stimulating this glucose rise in the bloodstream, exposing the blood vessels to

00:04:39.040 | that glucose.

00:04:40.040 | You're going to be turning on all the pathways with insulin to basically store it, and so

00:04:44.760 | it's strain for the body.

00:04:45.840 | And so I think giving the body times intentionally to allow insulin to come down and to allow

00:04:54.200 | glucose to come down, what that does is it generates metabolic flexibility.

00:04:58.880 | It gives our body an opportunity to have space to use accessible glucose and then convert

00:05:06.440 | into using stored fat, and that ultimately is metabolic flexibility, the ability for

00:05:12.160 | the body, giving the body opportunities to use glucose but then have times when there's

00:05:16.320 | not high glucose and insulin around to actually get into the fat stores.

00:05:22.080 | And I think one of the reasons why we have such a massive overweight and obesity rates

00:05:28.760 | in the country is because with the way the culture of eating right now, 11 eating events

00:05:34.200 | per day, eating over the course of 15 hours per day, I would imagine the average American

00:05:38.160 | body is rarely, if ever, tapping into their fat stores for energy in a meaningful way

00:05:44.520 | because we always have glucose available to the body.

00:05:48.560 | If you think about, again, the stats about ultra-processed food, about 70% of the items

00:05:54.680 | on the shelves in the grocery store are ultra-processed food, and those ultra-processed foods are

00:05:57.920 | built on refined added sugars and refined added grains.

00:06:01.880 | So we're just – we very rarely give the body the opportunity to rest and move into

00:06:05.840 | fat burning.

00:06:06.840 | And that's where compressing the eating window can be valuable.

00:06:11.800 | Obviously, people have talked about this before, but fasting can be a stressor for the body,

00:06:18.560 | especially if your body is not used to using fat for energy.

00:06:22.680 | And so it's something to ease into and go slow.

00:06:24.880 | But I think if you're slowing down enough to really hear what your body's signal

00:06:28.920 | are saying, you can kind of know whether I think your fasting is working for you or not.

00:06:34.880 | I can tell.

00:06:35.880 | If I've got too many other things going on, I haven't slept well, a lot of stress,

00:06:39.960 | I can tell that fasting is kind of making me jittery and not feel good versus if I have

00:06:44.600 | good capacity, I can feel that it's actually making me feel really incredible.

00:06:48.280 | And so tune in with your body, obviously, and you can check your biomarkers.

00:06:52.600 | If you have a CGM on, you can see what's happening in your glucose.

00:06:55.160 | If you have a ketone monitor, you can see what's happening in your ketones and really

00:06:57.800 | actually track, which I think makes fasting actually even more fun.

00:07:02.680 | I'll mention one other piece of data that I think is actually really kind of fun as

00:07:06.480 | well with timing of eating.

00:07:09.160 | There was a study that looked at people who ate the exact same meal at 9.30 a.m. or 8.30

00:07:15.840 | p.m., so basically after dark, essentially in the part of the diurnal phase when we probably

00:07:20.600 | shouldn't be eating versus early in the morning, 9.30.

00:07:26.120 | And the glucose and insulin responses for the same meal at 8.30 p.m. were significantly

00:07:31.580 | higher than when eating at 9.30 a.m.

00:07:34.160 | And so again, bang for your buck.

00:07:36.280 | It appears that eating in that earlier part of the day when we're active and our chronobiology

00:07:41.680 | is set up for metabolism and activity, we have a lower glucose and insulin response.

00:07:48.840 | There's also some evidence that melatonin, which is secreted as we get closer to sleep,

00:07:55.760 | has somewhat of an effect on impairing our insulin sensitivity transiently.

00:08:00.360 | And so we may actually just be not absorbing the glucose from those meals effectively later

00:08:04.680 | at night.

00:08:05.680 | So I tend to kind of move a little bit more low-carb, I would say, throughout the day

00:08:11.040 | based on that data and what I've seen on my continuous glucose monitor, basically just

00:08:14.920 | higher spikes for the same meal later in the day.

00:08:17.380 | So why not just kind of move it up earlier?

00:08:28.040 | [BLANK_AUDIO]

Fasting & the Best Times to Eat | Dr. Casey Means & Dr. Andrew Huberman

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