The Art of Manliness - When to Eat — The Optimal Schedule for Metabolic Health

00:00:00.000 Brett McKay here, and welcome to another edition of the Art of Manliness podcast.

00:00:11.520 When it comes to weight management and all-around good metabolic health,

00:00:14.840 we most often think about what to eat.

00:00:17.020 Well, my guests would say that it's also a crucial thing about when to eat.

00:00:20.860 Emily Manoogian is a chronobiologist and clinical researcher

00:00:23.620 at the Salk Institute for Biological Studies.

00:00:26.220 Today on the show, Emily shares how to create an optimal schedule 0.94

00:00:29.000 for a healthy metabolism by aligning your eating schedule with your circadian rhythm.

00:00:33.160 She explains when to start eating after waking,

00:00:35.580 when to stop eating before bed,

00:00:37.380 the importance of sticking to a set schedule,

00:00:39.400 and what happens to your metabolism when you don't follow these timing guidelines.

00:00:42.920 We also talk about how to best distribute your calorie intake throughout the day

00:00:45.700 and how to eat to mitigate the metabolic problems that come with being a shift worker.

00:00:49.880 After the show is over, check out our show notes at aom.is slash whentoeat.

00:00:59.000 All right, Emily Manoogian, welcome to the show.

00:01:07.600 Thank you for having me.

00:01:08.680 So you are a circadian rhythm researcher.

00:01:10.980 You research all the rhythms that happen in our body from sunup to sundown

00:01:15.880 and then in between, too, while we're sleeping.

00:01:18.180 How did you get started in that?

00:01:19.660 And what led you to focus on the intersection between our circadian rhythm and eating?

00:01:24.960 Yeah, so this started quite a while ago when I was an undergrad in college,

00:01:30.540 and I actually took a class called Hormones and Behavior

00:01:33.520 with Lance Kriegsfeld at UC Berkeley, and I was instantly enamored.

00:01:38.460 I was just fascinated with the subject that all of these rhythms control everything within our body,

00:01:43.860 and that wasn't even the biological rhythms class,

00:01:45.740 but it started to touch on rhythms because of seasonal reproduction in animals.

00:01:50.160 And I fell in love with it so much, I bothered him until he let me into his lab.

00:01:54.600 I took his next course on biological rhythms, and I was kind of hooked.

00:01:57.840 So then I did my PhD in neuroscience and behavior with Eric Bittman out in UMass Amherst,

00:02:04.160 again, with kind of a neuroendocrine focus,

00:02:06.120 but I really got into hardcore circadian biology at that point,

00:02:09.900 trying to understand this mutant hamster that could like phase shift 12 hours over a night,

00:02:14.940 like think like you could go to India and have no jet lag.

00:02:18.520 And so I was trying to understand how this worked.

00:02:20.600 And, you know, it always comes back to the molecular clock, which was really kind of cool.

00:02:26.080 But in that time, I realized I really wanted to use my knowledge of circadian rhythms to kind of

00:02:31.740 apply it to humans and to help other individuals,

00:02:34.540 because the only reason I knew all about this was because I was taking these very specific courses,

00:02:38.680 and it really wasn't public knowledge.

00:02:40.960 And I thought that was kind of crazy.

00:02:42.240 And so I had this amazing opportunity to come to the Salk Institute to work with Sachin Panda,

00:02:48.220 who mainly does wet lab and kind of basic science,

00:02:52.420 but had gotten into time-restricted eating through rodent studies,

00:02:55.520 and it was just about to start clinical work.

00:02:58.140 It just done one study kind of as a pilot and brought me on to get into this whole new field

00:03:03.920 and really kind of understand how timing of eating affects human performance and human health.

00:03:09.880 And I've kind of been doing it ever since.

00:03:13.040 A while back ago, we had circadian researcher Russell Foster on the podcast to discuss circadian rhythms,

00:03:18.460 but something we didn't dig much into is the relationship between circadian rhythms and our metabolism.

00:03:25.580 And I want to make that the focus of our conversation, because it's just really fascinating.

00:03:29.460 Can you walk us through the metabolic changes our body goes through during a 24-hour period?

00:03:35.800 Yeah, absolutely.

00:03:36.600 And caveat to this is, you know, when you're talking about metabolism,

00:03:39.720 it's not like you're only talking about the stomach or the gut or, you know,

00:03:43.540 it's your whole body works on metabolizing things.

00:03:47.340 I mean, you could think of muscle as your biggest kind of metabolic organ in a lot of ways.

00:03:51.360 So it's really kind of this whole body system.

00:03:53.600 And the circadian system controls pretty much every organ in your body.

00:03:57.140 So when you're sleeping, your body's trying to, hopefully you're fasting as well.

00:04:02.780 And we'll kind of circle back to this.

00:04:03.880 We'll kind of walk through a day.

00:04:04.860 So when you're sleeping, hopefully you're fasting and your body's actually able to break down fats

00:04:09.280 that you've built up over time or during the day and release glucose into your body.

00:04:14.480 Because if you're fasting at night, you're not taking in new sugars and your body and your brain

00:04:18.880 still need glucose to work.

00:04:21.000 And so you need some glucose in your body and going through your blood.

00:04:24.860 And so your fat can be broken down.

00:04:27.620 Glucagon is released to try to get that back into your blood.

00:04:30.900 When you wake up, you actually have this little spike in cortisol just before you wake up.

00:04:35.940 And that kind of helps your body wake up for the day.

00:04:38.480 You also get your sharpest rise in blood pressure.

00:04:40.820 And that kind of wakes your body up.

00:04:43.820 And for some people, this can also, you'll also see like a little increase in glucose

00:04:47.660 in the blood just from getting up and starting to walk around because your muscles need that

00:04:51.580 glucose.

00:04:52.080 So sometimes it can rise just a little bit because of that.

00:04:55.140 Then you're really alert in the morning.

00:04:57.220 Your brain is very capable.

00:04:58.720 Your body's starting to get going.

00:05:00.600 And your circadian rhythms have also organized, you know, worked with your liver to create enzymes

00:05:05.900 to be able to break down food.

00:05:07.160 So you're actually very able to break down food and digest a high amount of calories in

00:05:12.540 the morning.

00:05:12.920 So we generally think kind of like an hour or two, maybe three after you've woken up is

00:05:18.120 probably the best time to be able to process a big meal without having giant glucose spikes

00:05:22.840 or any other kind of negative consequences because your body's really up and moving.

00:05:27.020 And then throughout the day, while you're active, your body is still very able to digest a lot

00:05:32.640 of calories, a lot of different types of macronutrients.

00:05:36.100 And that's really kind of when you should be eating is when you're active.

00:05:39.160 As you get later in the day, you know, again, having your last meal in the early evening or

00:05:44.920 even, you know, not too late into the night where you're getting too close to bed is not

00:05:49.280 too big of a problem.

00:05:50.060 But the issue becomes is when people don't eat much during the day and then eat this huge

00:05:54.520 meals at night and you're really not able to process these really huge meals at night

00:05:58.540 or very late at night because your body's starting to get ready for rest, meaning it's

00:06:03.040 not producing all the enzymes you would need to break everything down.

00:06:06.160 It's not going to be able to use up all those calories you just ate.

00:06:09.140 And a lot of times after dinner, people are sitting down, you know, they're not really

00:06:12.420 going to be using a lot of that.

00:06:14.100 And when that happens, that becomes a little bit of a problem for it just kind of staying

00:06:18.520 in your body, not being fully processed.

00:06:20.200 And then you're not going to get to break down those fats at night.

00:06:22.300 The other thing that's happening at night is melatonin starts to get secreted and melatonin

00:06:27.980 is really inhibited by light.

00:06:29.540 This is why it happens in the evening.

00:06:31.660 It also is regulated by the circadian system and melatonin helps you fall asleep.

00:06:36.240 It also helps coordinate your metabolism by suppressing insulin secretion.

00:06:41.620 So if you're eating really late at night when your body is tired and it's dark, you don't

00:06:45.940 have insulin in your blood to be able to take that glucose out of your blood and pack it

00:06:50.140 away.

00:06:52.480 And so this is why when you eat a lot right before you go to bed, your glucose levels will

00:06:54.460 actually go really high and stay high sometimes for many hours.

00:06:58.140 And that will completely inhibit any fat breakdown or anything like that.

00:07:02.580 So depending on when you eat will kind of change what your body's doing at different times

00:07:07.540 of day.

00:07:07.920 But if you consolidate your food to your active phase, then you can kind of fast and break

00:07:12.440 down fats at night and use up a lot of the fuel you're taking in during the day.

00:07:16.800 That's really interesting.

00:07:18.180 I want to go back to when we're sleeping.

00:07:20.600 So when we're asleep, our body primarily uses, it's breaking down fat.

00:07:24.760 There's a process where your body can turn fat into glucose. 0.75

00:07:27.960 What's it?

00:07:28.480 What's the name for it?

00:07:31.500 Gluconeogenesis.

00:07:32.480 Gluconeogenesis, right.

00:07:33.880 But I also know that our body stores glucose in our liver.

00:07:38.800 Does our body use that glucose supply when we're asleep?

00:07:42.620 Yeah, so you can release glucose from your liver.

00:07:46.880 Absolutely.

00:07:47.960 And one of the problems with getting too much glucose or having highly high levels or not

00:07:52.460 being able to break things down is over time, you can also get fatty liver disease.

00:07:57.540 And this is really tricky because we know it's a common problem, but it's not very often assessed

00:08:03.140 just because the testing for this is quite invasive.

00:08:05.700 And there's not really much you can do about it aside from healthier diet and also, I would

00:08:11.700 say, eating at the right time of day.

00:08:13.240 But research is going on to really determine how effective that is.

00:08:16.520 But you can get this fatty liver disease where if you don't use up a lot of these sugars that

00:08:22.220 are in your liver, you can develop fat deposits within the liver.

00:08:26.060 And over time, that makes it so the liver doesn't function properly.

00:08:28.780 I know some people, particularly with like their pre-diabetic, when they wake up or even

00:08:34.860 like before they wake up, they have like a huge glucose spike.

00:08:38.180 Like it can like be 120 when they hadn't eaten anything in hours.

00:08:43.460 What's going on with the metabolism to cause that?

00:08:47.340 Yeah.

00:08:47.900 So when you get into things like pre-diabetes or type 2 diabetes, you know, it's not a normal

00:08:53.320 system anymore.

00:08:54.160 It's not like it's just higher levels of the same system.

00:08:57.920 That means that the glucose regulation is compromised and there's not one way that it

00:09:02.660 can be compromised.

00:09:03.640 In type 2, there's many different subcategories and there's different mechanisms for why that's

00:09:08.520 happening.

00:09:09.020 So depending on the individual, I could give you a different answer.

00:09:12.520 But you do see this in some individuals where when they first wake up, especially sometimes

00:09:17.560 when they go for a walk, they all see this big jump.

00:09:19.860 And I've seen this in individuals with, you know, women with gestational diabetes, sometimes

00:09:24.420 like they were taking their finger pricks and they would go for a walk first and that

00:09:28.080 would actually cause their glucose to spike.

00:09:29.960 And part of that is, you know, your muscles and stuff do need glucose.

00:09:34.600 And so you do naturally get a small amount of glucose increase by just, you know, getting

00:09:38.660 up and being active.

00:09:40.300 But in those individuals, it's kind of the system's over responding.

00:09:44.000 And this is where you have some type of insulin resistance or you have some type of other issue

00:09:51.140 going on that's causing the glucose regulation to be maladaptive.

00:09:56.100 So when we're waking up, we have an initial glucose spike.

00:09:59.200 It's not too much.

00:10:00.220 If you're healthy, it's not going to be huge, but it's just enough to get your body going.

00:10:04.700 And then the circadian rhythm is also going to start to bring on the insulin system.

00:10:10.960 So, you know, insulin might not be ready for you to eat, you know, pancakes and syrup right

00:10:15.800 off the bat.

00:10:16.640 It might take an hour or two before your pancreas is really pumping insulin out so you can start

00:10:21.340 shuttling glucose into your muscles.

00:10:23.960 Yeah.

00:10:24.160 And part of that is melatonin suppressing insulin, right?

00:10:26.880 So melatonin, we think of it at night, but it peaks like in the middle of your night.

00:10:31.520 And so it's still pretty high for a while.

00:10:33.940 And so it needs to come down.

00:10:35.740 So things like getting a lot of really bright light in the morning and letting your body wake

00:10:39.760 up for like an hour, that melatonin will then, you know, have plenty of time to shut

00:10:43.680 down.

00:10:44.080 Your body is ready to eat, which is why we usually recommend waiting at least an hour

00:10:47.640 after you wake up to eat.

00:10:49.040 So your body is able to process that because people think about late night eating being

00:10:54.020 a problem.

00:10:54.500 And I think it really is.

00:10:56.100 But super early eating is also a problem.

00:10:58.460 And I think you see that more in individuals that might have a really early commute and have

00:11:03.040 jobs where they can't eat on the job.

00:11:04.720 You know, I see teachers doing this a lot where they're like, well, I got to eat breakfast,

00:11:08.040 but they end up eating breakfast like in the dark at like five in the morning.

00:11:11.960 And that's not healthy either.

00:11:14.360 Okay.

00:11:14.500 So we still have some melatonin in our system when we first wake up and that suppresses

00:11:18.980 insulin production.

00:11:20.380 And then as the day progresses, your metabolism is turned on and you start releasing insulin.

00:11:25.920 And then as we get closer to night, melatonin is increasing again, which tells insulin production,

00:11:33.020 all right, it's time to go to sleep.

00:11:34.760 We don't need you anymore.

00:11:35.600 And then you're going back through that sleep process.

00:11:38.780 So how can we put these pieces together and use this information of how our circadian rhythm

00:11:44.580 manages our metabolism to optimize metabolic health?

00:11:49.820 Yeah.

00:11:50.060 So, I mean, when it comes down to it, it's kind of obvious things when you think about

00:11:53.780 it.

00:11:53.960 It's allowing your body to fast at night and really eating when you're active.

00:11:59.820 And that sounds extremely simplified, but that's kind of what the answer is, right?

00:12:04.280 So how you actually would apply that.

00:12:07.040 So we study a dietary intervention known as time-restricted eating.

00:12:11.660 Some people consider it a form of intermittent fasting.

00:12:14.900 Unlike other forms of intermittent fasting, it doesn't require any type of caloric restriction.

00:12:19.600 It can be combined with it, but it's not required for it.

00:12:22.460 And really it's just eating at the same eating window.

00:12:26.420 So usually an eight or 10 hour eating window.

00:12:28.960 So for example, 9am to 7pm, but it should be customized to your schedule.

00:12:33.920 So someone who wakes up at 6am every day is going to have a different eating window than

00:12:37.820 someone who wakes up at 9am every day, right?

00:12:39.760 It should be adjusted to fit your schedule and it should be the same eating window every

00:12:44.240 day.

00:12:44.520 And the way we'd say to usually figure that out is think about what your normal sleep

00:12:49.340 times are.

00:12:50.160 Hopefully you're at least trying to sleep for eight hours a day.

00:12:53.420 You know, a lot of us don't get that, but that should at least be the goal.

00:12:56.180 And then say, wait at least one hour after you wake up and stop eating at least three hours

00:13:01.660 before you go to bed.

00:13:02.980 That gives you now a 12 hour window and then pick the 10 hours that work for you.

00:13:07.760 And usually that's decided by a family meal and kind of working backwards that way.

00:13:13.460 And just that simple thing of saying, I'm going to eat at the same times.

00:13:16.680 I'm going to give that cue to my circadian rhythms that when I eat, I'm telling all the

00:13:20.900 clocks within my body, what time it is just through nutrient availability and the stimulation

00:13:26.240 that food gives to your brain as well.

00:13:27.820 But now you're saying, okay, here's a regular cue.

00:13:30.920 My circadian rhythms can rely on that.

00:13:33.260 And then the really cool thing about the circadian system is that it's anticipatory.

00:13:37.760 It's not a reactive, like you ate and so now I'm going to do something.

00:13:40.880 It's, I know you usually eat at this time, so I'm going to prepare enzymes to be able

00:13:45.260 to break down food for you at that time.

00:13:47.840 And so if you eat at regular times, your body will be more prepared to break down food at

00:13:54.460 that time and process it properly.

00:13:56.140 And then getting a regular fast that's long enough for your body, you know, at least like

00:14:00.520 a 14 hour fast each day.

00:14:02.620 I mean, most of that's while you're asleep, but getting that daily fast is super important.

00:14:07.760 So you can actually break down fats and use up sugars.

00:14:11.780 So you're not creating this, you know, overload of resources that your body can't handle.

00:14:17.500 And over time leads to a lot of issues.

00:14:19.360 Yeah, that sounds about what I do with my schedule.

00:14:21.140 So I wake up at 5.30 and then I don't eat until seven and then eat during the day.

00:14:27.080 And then our dinner is usually around 6, 6.30 and then nothing after that before I go to bed.

00:14:32.900 Yeah, I think that's pretty reasonable.

00:14:34.820 You know, I mean, that's like what, 11, 11 and a half hours.

00:14:37.220 But even with that, I don't think it's hurting you in any way.

00:14:40.820 You're aligning it to your active phase.

00:14:42.440 You're waiting until you wake up.

00:14:43.640 You're getting, you know, at least probably a three hour chunk before you go to bed.

00:14:47.580 I think that's absolutely fine.

00:14:49.400 Like, I think that's a very reasonable way to eat.

00:14:51.920 And you're aligning that with all the other cues that you're giving your body,

00:14:55.460 like light and activity and social interaction and stress and exercise.

00:14:59.260 Like all those other things are aligning so your body actually knows what time it is.

00:15:02.980 And just the simple act of supporting your circadian rhythms is super helpful for almost

00:15:09.740 every aspect of physiology.

00:15:12.180 Okay, so you want to have your first meal at least an hour after you wake up and then

00:15:16.540 stop eating three to four hours before you go to bed.

00:15:19.640 So you're aiming for an eight to 10 hour eating window overall.

00:15:24.700 And what this does, it ensures you're eating when your metabolism is most active and then

00:15:30.080 fasting when it's less so.

00:15:32.820 And also the other takeaway too is you want to eat at the same consistent times every day

00:15:37.880 because that helps your body be prepared to process food.

00:15:40.880 So you mentioned that there are some people who don't stick to the sort of time restricted

00:15:45.680 regular schedule.

00:15:46.920 What happens to our metabolism whenever we eat too soon after waking up and then eat

00:15:53.440 too late before going to bed?

00:15:55.880 Yeah, so part of this gets back to melatonin again, right?

00:15:58.160 When you eat too soon, you just might not have insulin enough in your system where your glucose

00:16:03.780 levels can get very high.

00:16:05.400 This is also a more common problem in the United States because a lot of our breakfast and not

00:16:10.340 just the United States, but it tends to be a bigger issue here.

00:16:13.320 A lot of the Western breakfast is very carb heavy.

00:16:17.040 And there's also been some really interesting science into like food desires at different

00:16:22.340 times of day.

00:16:23.320 And the things that we crave when we're tired, like late at night or early morning are not

00:16:28.400 healthy foods.

00:16:29.280 We do not crave a salad or, you know, like just avocados in the morning.

00:16:34.940 We crave a donut or a sugary coffee or something to give ourselves a treat because we had to wake

00:16:41.400 up and we're so tired.

00:16:42.440 So we try to treat ourselves with these really unhealthy foods.

00:16:46.340 And at those really late times, we're specifically not able to eat, you know, process them properly.

00:16:52.200 So eating super early in the morning, again, you're just going to have higher glucose response.

00:16:57.660 It's probably going to stay higher for longer.

00:16:59.780 Same thing at night.

00:17:00.820 When you're eating really late at night, you get that same kind of thing.

00:17:03.760 What's really interesting though, and some really beautiful science has come out in the

00:17:08.260 past couple of years for multiple groups now, but Frank Scheer's group at Harvard did

00:17:12.160 this really nice study where they had participants in the lab and they provided meals to them.

00:17:18.080 And they'd either give them dinner at 7 p.m. or to another set of participants, they would

00:17:22.960 give them dinner around 10 p.m.

00:17:25.880 And it was the same quality of food.

00:17:28.120 But the participants that got it really late not only had a higher glucose response, but they

00:17:33.320 stayed to have elevated glucose responses for hours later into the night.

00:17:37.540 And what was really interesting is even though they eventually got back down to normal fasting

00:17:42.360 glucose levels, but the next morning they gave them a glucose tolerance test and the ones who had

00:17:47.300 eaten the night before later, they didn't respond to glucose as well the next morning either.

00:17:52.780 They had a higher response to it and it stayed elevated longer.

00:17:55.920 And there's some nice work from Australia that came out also recently doing this in-lab model

00:18:01.160 of shift work where they had people do simulated night shifts and either eat a large meal, a

00:18:06.920 small meal, or nothing during the night while they were working.

00:18:10.440 And even though they were active, that eating during the night led to compromise glucose the

00:18:14.480 next morning in both groups that had any kind of food, but it was worse in the larger meal.

00:18:18.960 So it seems like eating really late at night compromises both the glucose at that time and

00:18:24.940 while you're sleeping, which can also cause you to have a worse quality of sleep, which

00:18:28.980 has its own downstream effects.

00:18:30.960 But it also compromises your glucose the next day and potentially for multiple days after.

00:18:36.720 So it really does seem to be throwing off the system in a pretty significant manner.

00:18:40.920 And this constant disruption to glucose regulation, constant levels of higher glucose, I mean,

00:18:46.280 that leads to pre-diabetes and type 2 diabetes.

00:18:50.080 And it sounds like too, if you're managing pre-diabetes or type 2 diabetes, you have to

00:18:53.860 think maybe what this research suggests is not only think about the type of foods you're

00:18:56.940 eating, but like when you eat them can have a big influence as well.

00:19:00.580 100%.

00:19:00.980 Yeah.

00:19:01.780 Yeah.

00:19:02.140 I've seen firsthand how timing your food intake can change how your body responds to it.

00:19:07.540 So a while back ago, I tried out the continuous glucose monitor.

00:19:10.920 I don't have pre-diabetes or anything, but I wanted to try it out.

00:19:13.800 And something I saw was when I was doing it, my first meal would be very carb heavy.

00:19:19.820 It's like a bowl of oatmeal and some yogurt and some blueberries.

00:19:23.220 And my glucose would just spike and it would stay spiked for like a really long period of

00:19:27.940 time.

00:19:28.680 So something I did is I swapped to a kind of a lower carb meal.

00:19:33.040 So it was just like eggs, some, yeah, it's just basically eggs and like a low carb wrap.

00:19:37.820 And I moved my oatmeal later in the morning and then like, yeah, the carb spike went away.

00:19:43.820 And then after I had my oatmeal later in the morning, I didn't have the same sort of spike

00:19:48.800 as I had when I ate it first thing in the morning.

00:19:51.460 Yeah.

00:19:52.060 I've seen that so many times.

00:19:53.920 And you know, the really great thing about continuous glucose monitors, or I'm probably

00:19:58.500 going to say it shorthand.

00:19:59.300 And so they're also called CGMs is they tell you so much about how you specifically like

00:20:05.360 you as a person respond to different foods because it's different for different people.

00:20:10.100 And just like you said, the same food can cause a different reaction at different times

00:20:13.980 of day.

00:20:14.920 And being able to wear a continuous glucose monitor is really powerful because you can

00:20:19.500 learn so much about yourself.

00:20:20.960 You might learn like, just like you said, you can eat oatmeal, just not first thing.

00:20:24.620 You have to eat it a little later.

00:20:25.720 Or that same might be true for a donut, or maybe you can't have it early, or maybe you

00:20:30.820 can't have it late, but in the afternoon, maybe it's not as bad for your system, you

00:20:34.460 know, or people find out like, maybe they really have big spikes in response to rice.

00:20:39.740 And you might have someone else eating the exact same meal that doesn't have that same

00:20:42.940 response, even at the same time.

00:20:44.600 There's individual differences between people, but usually people have something that gets them,

00:20:49.920 whether it's rice or pizza or donuts or oatmeal or whatever it is, or sugar in their

00:20:55.040 coffee, but knowing what your cues are is super important.

00:20:58.320 Because then you could say, okay, I need to either just really make sure I eat this food

00:21:02.420 at the right time, or maybe I shouldn't combine these two foods that are both kind of spikes

00:21:06.780 for me.

00:21:07.340 But that kind of personalized information, I think, is where this field is really going

00:21:11.540 to really understand like, these general rules are nice, but like you, you know, if you

00:21:16.900 are going to have a piece of cake or a donut, or even a bowl of oatmeal, there's a time

00:21:20.980 of day that's probably much healthier for you than others.

00:21:23.400 We're going to take a quick break for your word from our sponsors.

00:21:29.260 And now back to the show.

00:21:31.020 There's a saying, it's eat breakfast like a king, lunch like a prince, and dinner like

00:21:36.220 a pauper.

00:21:36.920 So the idea is you eat more of your calories, you know, at the beginning of the day, and

00:21:39.860 they start tapering off as you get towards dinner time.

00:21:42.900 Does science back up that adage?

00:21:45.640 Yeah, I think there's still more to be done in the field, but what we do know of it does

00:21:50.840 seem to be pretty true.

00:21:51.920 I think there's a little bit of debate if it's breakfast like a king, or I would argue

00:21:57.560 for some individuals, especially depending on your schedule, maybe lunch like a king

00:22:01.760 would also be fine.

00:22:02.760 But I think it's pretty well agreed upon now that a majority of your calories should be

00:22:08.000 consumed in the first half of your day.

00:22:10.380 And then your dinner should be probably a lower carb, higher protein, high fiber, but a more

00:22:16.160 modest meal.

00:22:16.860 And I think a lot of the evidence that has come out about like breakfast is so important

00:22:21.320 or late night eating is really bad.

00:22:23.840 I think both of those things have been true, but most of it is to avoid this late night binge

00:22:28.740 eating.

00:22:29.640 And I think a lot of times we see like in modern society, especially among like college students

00:22:35.500 or young adults, or I don't know, even working parents, people get really busy during the

00:22:40.340 day, they grab something really small for breakfast, they might not have chance to eat

00:22:44.860 much for lunch.

00:22:45.600 And then they go, Oh, I barely ate today.

00:22:47.100 And then they come home and they eat some huge amount of food at night and then relax.

00:22:51.900 That is obviously very bad for your system.

00:22:54.320 I mean, for all the different reasons, you're like starving yourself, your body then overeats,

00:22:58.220 then you're just sitting on it.

00:22:59.260 You have these really high levels of glucose, you're probably having a lot of fat buildup.

00:23:04.680 And so those, you know, the opposite of that is definitely a problem.

00:23:07.900 And I think a lot of evidence has actually really backed up that eating a larger meal in

00:23:12.180 the first half of your, you know, larger meals in the first half of your day and eating a

00:23:15.980 more modest dinner really does kind of help support the circadian system and it helps support

00:23:20.960 good, you know, metabolic health.

00:23:22.600 So you don't want to eat too late in the evening, you know, before you go to bed because your

00:23:27.460 body's kind of going to sleep, insulin production is going down.

00:23:30.480 If you eat later in the night, it's going to cause blood sugar problems, could possibly

00:23:35.960 potentially lead to weight gain.

00:23:37.440 It can also just disrupt sleep, right?

00:23:39.600 Because you're just, you've got this big ball of food in your stomach and you're trying

00:23:42.560 to digest.

00:23:43.620 But, you know, people in Europe, a lot of them, they seem to eat later in the evening

00:23:47.220 without any problems.

00:23:48.100 Like they eat dinner at nine o'clock sometimes.

00:23:50.120 What do you think is going on there?

00:23:52.600 Yeah, so that gets really interesting.

00:23:54.620 You know, you think of Spain, right?

00:23:55.820 Everyone thinks of Spain's eating super late.

00:23:57.820 I remember the first time I went there, we went out to go eat dinner at like eight and

00:24:01.620 it was completely empty and I was very confused and no one showed up till like nine or ten.

00:24:05.800 And that was kind of mind-boggling to me.

00:24:08.680 And as a circadian researcher, obviously I was curious about this.

00:24:13.060 A lot of this is they actually have exposure to sun at pretty different times of day.

00:24:17.920 They're actually pretty delayed.

00:24:19.480 And if you switch the clock on the wall to align with when they actually see light, it's

00:24:25.500 actually not very late for them.

00:24:27.300 And this becomes an issue in different parts of the world where there's these really large

00:24:31.760 time zones that span large areas.

00:24:35.040 And there's, you know, if you look at light availability in different parts of Europe,

00:24:39.280 it might say 6 p.m. on the wall.

00:24:41.760 And in one city, it might be completely sunny.

00:24:44.220 And in another city, it might be completely dark, you know, at the same time of year.

00:24:48.560 And so when we think about circadian rhythms, we think about time, like 7 p.m., 8 p.m.

00:24:53.580 These are usually they're clocks on a wall and they're not actually sun time, but our body

00:24:58.960 is responding to sun more than artificial light.

00:25:02.880 And so when you have these shifted, you know, light availability or sun availability,

00:25:07.700 you typically do get these shifts in behavioral patterns.

00:25:11.680 And Spain is a big one of those.

00:25:14.240 They also typically go to bed a little bit later.

00:25:16.820 They also usually have a siesta in the middle of the day where they get to take a break and

00:25:20.580 maybe a little bit nap.

00:25:22.120 And so they have kind of different overall schedules.

00:25:25.560 And so it's not the same like I ate at 9 p.m., but I have to go to bed at 10 p.m.

00:25:31.020 to get up to be able to leave super early in the morning.

00:25:33.440 Their schedule is a little bit delayed.

00:25:34.940 And their light is also a little bit delayed, which does account for a lot of those differences.

00:25:41.580 Okay, so that's interesting.

00:25:42.340 So there's no one size fits all prescription for this stuff.

00:25:45.820 It's like, well, you can only eat from this time to this time.

00:25:48.240 It's going to depend on one, you know, just the environment you're in, not only the physical

00:25:53.720 environment, how much sunlight you're getting, but also the social environment that can train

00:25:58.580 your circadian rhythm in a certain way.

00:26:00.660 But it also, every person has their own unique chronotype.

00:26:04.060 And there's some people who are night owls, like where they wake up later and then they

00:26:08.240 go to bed later.

00:26:09.140 So those individuals who are night owls might be able to eat later in the evening, 8 o'clock,

00:26:14.160 9 o'clock.

00:26:15.160 And they're not going to go to bed for three or four hours still.

00:26:18.620 And they're going to be fine.

00:26:19.440 They probably won't have any problems.

00:26:21.460 Yeah.

00:26:21.760 I mean, it gets a little complicated, right?

00:26:23.740 The problem with night owls are, and I tend to be a later person as well.

00:26:28.840 So no shame in saying night owl.

00:26:30.540 I know it can be, people kind of put it in a negative light a lot, and I don't think

00:26:34.100 that's fair.

00:26:34.920 The problem is, is that if you're staying up late, it also means you should be getting

00:26:39.860 up late and still getting light at a reasonable amount of light.

00:26:43.980 And if you're getting up super late or going to bed super late and you're not getting a

00:26:47.340 lot of light, that can lead to its own kind of issues.

00:26:50.440 And if you are, you know, eating really late after it's been dark for a very long time,

00:26:55.040 you still could potentially have some melatonin coming up where that's not the best situation.

00:26:59.240 And this also gets into if you really are a true late type or not.

00:27:03.700 And there's some interesting science here.

00:27:05.400 So there are circadian mutations that can make you an extreme morning person or an extreme

00:27:13.100 late person.

00:27:14.220 And these are not normal.

00:27:15.760 I like to stay up till midnight or one or even two.

00:27:18.020 These are like, I cannot fall asleep before three or 4 a.m.

00:27:21.260 And I have to wake up at like 11 or 12.

00:27:24.260 Or there are people like, I can't stay awake past 6 or 7 p.m.

00:27:29.040 And I have to wake up by 4 a.m.

00:27:31.240 Like these really intense differences.

00:27:33.380 Those are known genetic changes.

00:27:35.460 And there probably are some spectrum.

00:27:37.540 And your chronotype can oscillate a bit throughout your life.

00:27:40.800 You know, little kids tend to be earlier risers.

00:27:43.060 When you go through puberty, you tend to delay a bit.

00:27:45.380 And it kind of comes a little bit earlier.

00:27:46.940 And I think there are biological mechanisms for that.

00:27:49.280 But some really cool work has been done looking in different populations around the world,

00:27:55.160 comparing individuals that don't have electricity, that are living off of natural light and fire

00:28:01.060 light versus people living within 100 miles but have full electricity.

00:28:07.040 And they found the people that live without electricity go to bed earlier, like all of them.

00:28:12.120 They go to bed earlier.

00:28:13.360 They wake up earlier.

00:28:14.580 They adjust it with the sun.

00:28:16.060 And there's even a study done in Colorado that showed that if you take individuals and

00:28:22.300 you put them camping where they only have firelight for like a week or two weeks, that

00:28:26.800 they all become a little bit earlier.

00:28:28.740 And so we think a lot of the reasons why so many of us are later types is not just because

00:28:33.380 of our chronobiology, but because we get a lot of artificial light.

00:28:38.020 You know, after a long day's work, maybe you're also taking care of kids.

00:28:41.020 And then the kids go to bed and it's like, oh, I just want to relax for an hour and watch

00:28:44.840 the show and maybe you want to have a snack with it, you know?

00:28:48.280 And then it's like we get kind of our relief then.

00:28:51.440 And so we end up staying up later really through these choices to stimulate ourselves in that

00:28:56.160 way to give ourselves some kind of entertainment or whatnot, or just, you know, work or whatever

00:29:00.220 it is where we end up staying up later than our bodies probably would want to.

00:29:03.780 And so if you take a lot of that stimulus away, people generally tend to shift a little bit

00:29:08.700 earlier and that's not always possible to do.

00:29:11.620 But I think trying to kind of listen to your body more than your schedule or a clock on

00:29:16.080 the wall is not always the easiest thing to do, but it's probably much healthier for you.

00:29:21.920 You mentioned some research done on shift workers and how the circadian rhythm affects their

00:29:27.180 metabolism there.

00:29:28.240 I know I'm sure there's a lot of people listening to this podcast.

00:29:30.140 They might be a shift worker, maybe they're a first responder, a nurse, doctor, maybe they

00:29:34.460 just work a shift at a factory that's at nighttime.

00:29:37.840 What does the research say about how their irregular sleep schedule affects their metabolism?

00:29:45.040 Yeah, so I think shift work is so important to study.

00:29:48.620 And the crazy thing is they're almost never included in clinical trials.

00:29:51.940 I mean, it's like 0.0001% of clinical trials are including shift workers, even though they probably

00:29:58.140 have the biggest need.

00:29:59.960 And that's just because shift work itself is so confounding.

00:30:02.840 So like you said, obviously, if you're working in the middle of the night or working very late

00:30:07.280 or very early or having a moving schedule, your sleep is going to get disrupted.

00:30:11.980 Not being able to sleep adequate amount has also been shown to lead to weight gain, to lead

00:30:17.680 to increased glucose intolerance, higher A1C levels, which is, you know, when we talk about

00:30:22.840 hemoglobin A1C, it's like an estimate of like glucose for the past three months, but it's

00:30:26.880 kind of the gold standard.

00:30:28.360 All those things get worse when you have any form of sleep deprivation, even if you're still

00:30:32.580 sleeping at night, but it's, you know, really short sleeps.

00:30:35.880 The other thing that shift work does, though, is it really changes when you eat.

00:30:39.200 You know, if you're working a night shift, you're probably going to have to eat at night.

00:30:44.060 And that's kind of your functional time then, right?

00:30:47.200 But even though you're awake and you're active, your body's still not processing that food the

00:30:51.380 same way. And I think the best data we have from that is in like simulated shift work where

00:30:57.940 people are brought into the lab, given standardized meals, and you can see that they don't process

00:31:01.800 the food the same way. They do have higher glucose responses. They stay higher longer.

00:31:07.140 And then again, it's not just at that time. It's not just, oh, at night, my glucose was

00:31:12.420 compromised. The next day when you eat, your response to glucose is also compromised and you're

00:31:17.680 having poor glucose regulation. And so that's a really big problem we're trying to face.

00:31:23.520 In our own work, we did a randomized control trial in firefighters in San Diego County that

00:31:28.400 worked 24-hour shifts. We were able to put them on a time-restricted eating diet. I mean,

00:31:33.120 this was really mainly a feasibility study, but they were able to do it. Now, we started with them

00:31:38.120 because it's probably one of the easier shifts to do that with because they're working a 24-hour

00:31:42.020 shift. Their day is still their day. They're still mainly up. They might take a nap, but they're still

00:31:46.020 awake during the day. They eat lunch and dinner together. So they have pretty regular meals,

00:31:51.600 but they are working the full 24 hours. So they're getting on calls throughout the night. They're

00:31:55.720 getting woken up. All these other things are going on. And a lot of times they would get a snack in

00:32:00.080 the middle or people would bring in treats. So they were eating throughout the night, but they found

00:32:03.720 they were able to stop those extra eatings throughout the night. They were able to eat within a 10-hour

00:32:07.640 window. And of the participants who did have cardiometabolic disorders, we saw big improvements in

00:32:13.180 HbA1c. So glucose regulation, we saw improvements in diastolic blood pressure and overall energy

00:32:19.460 levels. People were feeling better. And so that was really exciting to see. And we even saw in the

00:32:24.600 full group, a decrease in very low density lipoprotein, which is kind of a worse version

00:32:30.060 of LDL cholesterol. When you think of that, it's like the bigger version of it that really leads to

00:32:35.120 these plaques in the heart. And we saw that those were getting smaller and that was really exciting to

00:32:39.600 see. And so I've recently been funded to do a new study in nurses and nursing assistants that

00:32:46.320 work night shifts. And we're trying to see if time-restricted eating is possible within that

00:32:51.300 group. And we're also trying to test out if a low glycemic snack at night may still give them some

00:32:57.240 benefits, even if it doesn't give them the full benefits, just out of feasibility alone. Because

00:33:02.640 the problem with working with shift work is we know it's bad for your circadian system,

00:33:06.520 but it's absolutely necessary. We need first responders. There's some jobs hopefully some

00:33:12.900 people don't have to do, but their most shift work is really out of necessity. And so we can't

00:33:18.340 change when they get to sleep. We can't change their light exposure most of the time, but we could

00:33:22.420 potentially change when they eat. And so we're seeing this as a potential window to be able to

00:33:26.920 help this extremely valuable group of people. Okay. So it sounds like if you are a shift worker,

00:33:32.700 the goal there is if you're staying up late at night or throughout the night, is it just to try

00:33:39.520 to eat during a 10 hour window, try not to eat at night and try to eat your calories during the day

00:33:43.820 when you can? Yeah. I mean, that's what we're trying to really figure out because there's just

00:33:48.400 not a lot of science there yet. I mean, theoretically, yes. I think the general logic and

00:33:52.760 based off the in-lab studies, which are only over a few days and very short periods of time,

00:33:57.200 but I think the logic really is that you're not able to process especially glucose more than other

00:34:03.100 macronutrients. And so I think having low glycemic snacks is probably going to be better. You know,

00:34:08.860 if you have to choose between a hard boiled egg and a big bowl of pasta, go for the hard boiled egg

00:34:13.940 or some nuts, something that could give you some energy and satiate you and maybe give you something

00:34:20.160 to nibble on because eating is also a big stimulatory cue for alertness. But yeah, lower glycemic foods,

00:34:26.900 smaller portions, so far it looks like that's what would be better if you can't just, you know,

00:34:33.400 completely fast at all. If you are able to fast through the night and keep a regular eating time,

00:34:38.840 you know, like to match with the days where you aren't working and eating normally during the day

00:34:44.080 and trying to keep to that, I think that's ideal. And then our hypothesis is that, yeah, really trying

00:34:48.880 to decrease the amount of carbs and decrease the total amount of calories that you're getting at night

00:34:53.260 would be kind of a good in-between compromise. Okay. So those are some general ideas, but I guess

00:34:58.040 more research is forthcoming. We'll have to stay tuned for that. You mentioned that time-restricted

00:35:02.700 eating can be seen as a form of intermittent fasting. How does intermittent fasting, I'm talking

00:35:08.880 like extended fast here, how does it affect our circadian rhythm or does it affect our circadian

00:35:15.200 rhythm? Yeah. So intermittent fasting is such a vague term. You know, it could mean a lot of

00:35:20.200 different things. I think the most common versions are like a five, two diet where five days a week,

00:35:24.280 you do whatever you want. And two days a week, you have pretty intense caloric restriction. And then

00:35:29.660 the other would just be like an eight hour, six hour diet, which is fairly similar to time-restricted

00:35:34.320 eating, but those usually don't keep a consistent eating window, which is really not the point I think,

00:35:40.880 which, you know, but the idea is usually of intermittent fasting is to decrease calories as well as

00:35:45.900 getting these longer periods of time where you're not eating. They can affect the system. I think of

00:35:51.360 them kind of like a cleaning out period of some sort. You know, if you think about nutrient

00:35:55.900 availability as a cue, eating all the time is kind of an abundance of cues. It's kind of constantly

00:36:01.160 resetting. Fasting kind of allows the natural rhythms to tick on their own a little bit more,

00:36:06.780 kind of continue on their own. Because if you had no cues, you still have these internal rhythms that

00:36:10.880 would keep a 24 hour day, but food and light are some of the biggest cues you can give your body.

00:36:15.420 So fasting kind of relieves that cue. And I don't really think of it as a way of setting the system

00:36:20.660 at all. I think having regular food timings are more important for that aspect of it,

00:36:25.140 but longer term, faster, you know, a couple of days or a day, or just these low calorie periods

00:36:30.880 can be helpful metabolically for other reasons, not via the circadian system. You know, you can get

00:36:36.480 some increased ketone production. You can relieve some other stress on the system. It's almost like a

00:36:41.840 rinsing out. And if you look at, I mean, so many different cultures have incorporated fasting

00:36:47.180 over, you know, hundreds of years. And a lot of them aren't complete fast, similar to intermittent

00:36:52.880 fasting. A lot of them are not water only. Most are not water only. Most are, you know, like nuts

00:36:58.820 or dried fruits are sometimes allowed or bone broths or different things like that to allow for really

00:37:05.080 small amounts of calorie intake for maintenance, but really just trying to allow the body to probably

00:37:10.160 break down more fats, kind of cleaning out the system of sorts. And those can be helpful

00:37:15.040 occasionally. You know, a lot of people try to practice something like that, like, you know,

00:37:19.080 three or four times a year, but I don't think them think of them as much as a circadian input as they

00:37:24.960 are. Maybe you're looking more at a metabolic fasting kind of ketone glucose regulation system

00:37:30.080 that obviously the circadian system is involved in, but it's kind of coming at that system from a

00:37:34.900 different angle. Gotcha. Well, let's do a quick recap. I think we've talked about a lot of

00:37:38.600 interesting things here. So I think the big takeaways is, you know, your body has a rhythm

00:37:43.060 and when we eat can influence how our body responds to food we eat depending on the timing of it. So

00:37:50.500 I guess wait about an hour after waking up to eat to let your body kind of wake up. That's the first

00:37:56.100 takeaway. I think another takeaway, maybe postpone carbs till later in the day, like lunch, maybe use

00:38:03.280 more of your carbs. And then as you get closer to nighttime, eat your last meal three to four hours

00:38:08.460 before you go to bed and you should be good. Yeah, I think that's the easy way of thinking

00:38:13.020 about it. And again, like, you know, like we just said, it's all relative to when you sleep. So

00:38:17.240 try not to look at a clock on a wall or say, I have to eat by five because someone said this. It's,

00:38:22.780 I got to eat when it's right for my body to eat. And that might mean little delays or little advances.

00:38:28.680 But I think when you're thinking about trying to adopt like a time-restricted eating or something

00:38:32.720 like that, it's never about meal skipping. It's never about these like huge,

00:38:37.200 I'm starving myself. It's really just about aligning your food to when you're active.

00:38:41.900 And if you're not eating till, you know, two hours after you wake up, it could probably have carbs in

00:38:46.380 it. It's more of a don't wake up and eat a ton of carbs right in the morning. And yeah, I think late

00:38:51.520 morning or early afternoon is probably a better time for carbs, like you said. But really, it's just

00:38:56.920 aligning when you eat to when you're active and allowing your body to get a proper fast at night.

00:39:02.140 Fantastic. Well, Emily, it's been a great conversation. Where can people go to learn more about your work?

00:39:05.220 Yeah, so you can follow me on Twitter at Emily Manugian. You can also look us up at the Salk Institute

00:39:12.460 website, or we have a app that we run that we use for all of our clinical trials. But it's also free

00:39:19.100 for the public. It's completely nonprofit research app. It's not commercial at all called My Circadian

00:39:24.600 Clock. You can find us at mycircadianclock.org. And the app is free to use on any iPhone or Android

00:39:31.540 phone. And on our website, we also just have lots of information about circadian rhythms,

00:39:36.960 about time-restricted eating, about healthy lifestyle. So yeah, you can check us out anytime

00:39:41.560 there. Fantastic. Well, Emily Manugian, thanks for your time. It's been a pleasure.

00:39:44.900 Thanks so much for having me.

00:39:47.040 My guest today is Emily Manugian. You can learn more about our work at salk.edu. That's S-A-L-K.E-D-U.

00:39:52.960 Also check out our show notes at awim.is slash whentoeat, where you can find links to resources

00:39:57.260 when we delve deeper into this topic. Well, that wraps up another edition of the AOM podcast. Make

00:40:09.080 sure to check out our website at artofmanlies.com, where you find our podcast archives, as well as

00:40:13.280 thousands of articles that we've written over the years about pretty much anything you think of.

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00:40:27.260 As always, thank you for the continued support. Until next time, it's Brett McKay,

00:40:31.040 reminding you to listen to the AOM podcast, but put what you've heard into action.

The Art of Manliness - November 06, 2024

When to Eat — The Optimal Schedule for Metabolic Health

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