How to Use Time-Restricted Eating to Reverse Disease and Optimize Health [transcript]

Written by Christopher Kelly

Aug. 21, 2018


Tommy:    Hello and welcome to the Nourish Balance Thrive Podcast. My name is Tommy Wood and today I am joined by Satchin Panda. Hi, Satchin.

Satchin:    Hi, Tommy.

Tommy:    Thanks so much for joining me. I'm a big fan of your work particularly because you sort of spanned from molecular biology to rodent studies to translation trials in humans. You have some great simple actionable advice in the field of circadian biology which is you're probably the preeminent expert in at the moment. I think that whole line of research is a really rare combination to have. I think that's fantastic.

    You're on the podcast because you have a new book called The Circadian Code, which I very much enjoyed. I've actually mentioned your work on the podcast multiple times. Hopefully, people will be roughly familiar with what you do. I won't get you to do a long and extensive bio. We can put that in the show notes. But maybe instead you could start with story of your grandparents and how that got you thinking about circadian biology and why the book is dedicated to them?

Satchin:    Yeah. Actually, I was lucky enough to be born in India in the '70s and have two different grandparents who are very different. My maternal grandparents, my grandfather worked at local train station as a goods clerk. He used to have night shift. I saw firsthand what is circadian disruption because whenever I wanted to play with him as a kid he was not there. He would come home in the morning and saw the disruption firsthand.

    In complete contrast, my paternal grandparents, they lived on a farm. They raised all of their food from the farmland and they did not have electricity for a very long time. They're mostly what I call day active that never had any circadian disruption. That was exciting to see this contrast. And then fast forward few years, my maternal grandparent, my grandfather had Alzheimer's and died in his early 70s and my maternal grandmother, who used to wait for my grandfather to come back from work and also had what I call now second hand circadian disruption had severe liver disease and she also died several years later.

    Whereas on my paternal side, although they lived in a village, very limited access to healthcare, I don't remember my grandfather ever taking any antibiotics or visiting a doctor but had fresh food and had a very strong circadian rhythm because every day he finished his dinner around sunset time, had a long night of sleep. He lived to be as of late 80s. That sparked some interest that was it just [0:02:51] [Indiscernible] experiments where on one side grandparents who had chronic circadian disruption died earlier and had very long end of the life illness, whereas on the other side who had very nice circadian rhythm had a prolonged life. That sparked initially my interest in circadian rhythm.

Tommy:    From that story of your grandparents, I think what's interesting to me having spent a significant amount of time in academia is that your training path to be a scientist, professor at the Salk Institute, was quite nonlinear. You started in agriculture school and then you got a research job at a flavor and fragrance manufacturer. If you compare that to somebody in the US who might go to do undergrad in genetics and then a PhD, another postdoc period and then go to some kind of professor position or something.

    Yours, you started a little bit further away and then obviously moved both fields and country. Do you think that you benefited from doing things a little differently?

Sathcin:    Yes, definitely. I always think some of the very foundational concepts that I use in my research, they were imprinted long time ago. For example, when I was working in International Flavor and Fragrance back in India, working with vanilla plants and seeing how they flower in the wee hours of the morning, that again reignited my interest in circadian rhythm.

    What is really interesting about circadian rhythm field is this is a field that is not dedicated to curing a disease. It's really dedicated towards understanding the timing mechanism in biological systems whether it is plant, a pond scum, insect like fruit fly, mouse or human. My exposure to these plant signs very early on actually helped me to appreciate this conjugation of principle at cross species so that when I was doing my PhD in plant circadian rhythm, that's when one of the genes that I was working on. It turned out to be a central player in connecting DNA damage response, metabolism and circadian clock.


    That was really exciting because at that time in 2001 very few people were thinking about circadian rhythm and metabolism or circadian rhythm and damage repair. Most people are trying to solve the mystery of circadian rhythm and maybe how it relates to sleep-wake cycle. My training through all this tortuous path actually helped me to have a much open mind about learning a principle in one system and trying to apply it in another system.

Tommy:    If we fast forward quite a few years to the work that you've become famous for most recently which is all your different time-restricted feeding studies in animals, lots of different diets, lots of different feeding strategies, could you talk a little bit about the studies that you've done looking at circadian timing and feeding in mice, at least to start with, because I know that's where you developed a lot of your work, and then how that might translate to improving health?

Satchin:    Yes. A few years ago when we're looking at mouse as a model system for metabolic disease, we noticed that there are nearly 11,000 papers describing when mice are given high fat diet or any unhealthy diet whether it's high fat, high sucrose, high fructose then within nine to 12 weeks mice become very unhealthy. That's the basis for almost all metabolism research about how diabetes, obesity, cardiovascular disease, those diseases develop or even various drugs that are used in modern days to treat those diseases suggested in this model.

    Actually, it was Joe Bass, another leader in circadian metabolism research, who made this very interesting observation in one of his 2007 papers showing that mice with ad libitum access to high fat diet, so that means when the food is given on the food hopper inside the cage they had access to food. Whenever they want they can eat. Then somehow they lose their circadian rhythm in eating. Mice are nocturnal. These will be eating at night time. But when mice are given this yummy food then they eat throughout the night.

    And that observation sparked an interest in me because I was thinking how much of this disease is due to bad diet versus how much of this disease is due to eating at the wrong time. We did a very simple experiment where we took group of mice born to the same mom in the same room who are completely identical in age, gender, everything, divided them into two groups. One group got to eat whenever they wanted this high fat diet. They were getting 65% of their calories from fat, 20-25% from sugar. We knew that these mice will become unhealthy, obese, diabetic, et cetera, within ten weeks.

    And then the second group ate the same exact diet, same number of calories every day, but in the fast experiment they were given that food within eight hours every night. Surprisingly, even after 18 weeks, we know that this high fat diet causes obesity within nine to ten weeks. We kept the mice up to 18 weeks on this diet. Mice that ate the same number of calories from the same food source but ate everything within eight hours were completely protected from obesity, diabetes, cardiovascular disease, signs of cardiovascular disease, et cetera.

    In fact, if we compare these mice with the mice that ate ad libitum or whenever they wanted, this time-restricted fed mice were 28% less. One would suspect that, well, this mice are going through 16 hours of fasting every night, maybe they're losing muscle mass. But surprisingly, most of the weight difference was due to fat mass. They had the same muscle mass. Both groups had the same muscle mass. The only difference was fat mass.

    This was so exciting at the same time terrifying because we are going to challenge one of the basic tenets in nutrition research that's a calorie is a calorie, whatever you take in, you got to spend, that I had to repeat this experiment three times with three different postdocs and every time the result came out the same. Then we published that paper in 2012.


    Then the question was: Was eight hours a magic number? The funny thing about the eight hours was the first graduate student who did the experiment, Christopher [0:10:06] [Indiscernible], who is now an assistant professor in UC Santa Cruz, that time he had a girlfriend who did not let him stay in the lab for more than nine hours. That's the reason why we did the experiment for eight hours. One interesting thing is although we published that paper and it was a prevention model, media and the press spun it as if people who are already overweight and obese if they eat within eight hours then they'll lose weight.

    Of course, that is not the experiment we did. This is an interesting example but the media interest and then the hype actually pushed us to go back and redo the experiment where we fatten up the mice first and then put them on eight hours or nine hours in the second experiment and we made sure that they eat the same number of calories and to our satisfaction we did see that these mice lost weight and their pre-diabetes or glucose intolerance went away and most of the weight loss was due to reduction in fat mass and muscle mass did not change.

    In the same experiment, we tried nine hours, ten hours, 12 hours and 15 hours. We found that up to 12 hours there is health benefit and 15 hours doesn't give you much health benefit. So, in that, these two papers established that at least the mice, feeding the mice within eight to 12 hours is a good thing to keep your pet mouse healthy.

Tommy:    So, can you give us some thoughts on how that translates to human time? Is eight hours in a mice eight hours in human or how do we go about maybe translating about some of those ideas across to the people listening to the podcast?

Satchin:    Yeah, so, one interesting thing is although mice and human weigh very differently and you might argue the metabolism is very different but there is only big thing that is common between mouse and humans, that is, both of them have the same 24-hour circadian rhythm. Since we are talking about biology of time we think that a lot of this nicely translates between mouse and human.

    The next challenge for us was to see when people eat because, again, we always tend to ignore the small amount of calories we eat here and there, one drink 100 kilocal beverage and think that is not going to do too much to the metabolism. That' not really true because, just imagine, in the daytime somebody comes and rings the calling bell and front door, it's okay, you'll go and set the call and open the door and see the person.

    Imagine, in the middle of the night, if someone rings the bell, that disrupts your sleep. It's a big thing. Next day we'll talk about that event. The same thing, when your system metabolism is in a resting phase and it's going through its repair and rejuvenation even if a small amount of food goes into the stomach then the whole system has to restart again to digest, process that food.

    We wanted to see when people eat so we made a very simple lab. Now, it is called my circadian clock where people take a picture of what they eat and since the picture has all the metadata, when, what, how much people eat, we process the data. The first iteration of that app we recruited around 56 people from San Diego area who are not doing shift work, not students, and we simply wanted to know when people actually eat.

    We know that people eat slightly differently at different time between days, between weekdays and weekends. Maybe two different weekends might be very different so we collected data from three weeks. What we found was very surprising. Although most of them said that they eat all their meals within maximum 12 hours. We found that only 10% of people actually eat all of their meals consistently every day within 12 hours period.

    50% of adults who were not even doing shift work, they actually eat within 15 hours or longer. That was really eye opening because then we thought, well, what we are doing has larger relevance to humans, because if these people who are eating for 14-15 hours or longer every day, if they reduce their interval to eight, ten or 12, maybe we'll see health benefits. In the first study, we took some of these overworked people and asked them whether it's a modifiable behavior they can stick to, say, ten hours eating for 16 weeks, four months.


    And we didn't tell them what to eat or how much to eat. They continued doing that. To our satisfaction they actually liked this idea. They adopted it for 16 weeks. They lost a modest amount of body weight, around 4% body weight, and then we let them free for the rest of the year. After one year when we brought them back, surprisingly, they were still sticking to the same habit.

    When we asked why they stuck to the habit, surprisingly, they told us that they sleep much better and they feel more energetic throughout the day. This is something that mice will never tell us. This was also verifying that this is a modifiable behavior that will self sustain for long period of time. This is very important in human translation, lifestyle research because you can come up with a lifestyle intervention but if it is not sustainable then it may not have that much impact.

    In the last few years now there are quite a few independent labs that have repeated our experiments both in mice and also in humans and gratifyingly all of them are reconfirming what we have said. What is really important is there are even some studies where people have tested this eight-hour time restricted eating on trained athletes who have already optimized their health, they're in their top performance, to see whether this will affect their performance and health.

    What is gratifying is it did not change their muscle mass because people will think that 16 hours fasting will reduce muscle mass in humans. They did not do that. It actually reduced, even if they had some amount of fat mass, it reduced their fat mass slightly. This is very good news for us because one of the questions I always get from people is maybe people will breakdown their muscle, which is not true.

    There are more controlled studies coming out of humans showing that it actually improves cardiovascular risk factors and might prevent or reserve pre-diabetes, improves glucose regulation, reduces inflammation. These are all coming from independent labs. That's very gratifying to us.

Tommy:    That's quite an extensive list of potential benefits. One of the things you mentioned -- The study mentioned, I remembered it's in -- I think it's in resistance training, so guys who are bodybuilding or something similar. A lot of the guys that we work with, a lot of the guys listening to the podcast, they're endurance athletes who may spend two or three hours a day training. One thing they often struggle with is getting in enough calories. I was wondering if you had any thoughts for people like that who have very high calorie needs that may struggle something in a given window?

Satchin:    Yeah. That's something, of course, my lab we haven't looked into it but what I hear from a lot of people who are doing endurance training, they benefit in slightly different ways. In most of our mouse experiments, when we did these mouse experiments, we had this muscle performance as one of the worries behind our back.

    We do something that mimics resistance training and endurance training. For resistance, we looked at their grip strength and the grip strength doesn't change. And for endurance, we put the mice on a treadmill and they'd run on this treadmill for as long as they can until they're exhausted they cannot run anymore. So, running to exhaustion.

    What was interesting was if we take mice that ate ad libitum, whatever they want, within eight hours, ten hours, 12 hours, and some mice that ate eight to nine hours during weekdays and ad libitum in the weekends, and then we had mice that had a very balanced diet whenever they want. Now, if you take the mouse that eats balanced diet whenever he wants then the mice runs around 75 minutes on this treadmill.

    The mice that ate unhealthy food whenever they want, of course, you would expect that mouse runs 45 minutes on the treadmill. What was surprising was that the mouse that eats the same high fat diet, eats within eight to ten hours can run on treadmill for 150 minutes, almost twice longer than the mouse that ate balanced diet whenever they wanted.

    We have repeated it almost in every paper and we find the same thing. But what is exciting is that the mouse that eats the same number of calories within 12 hours and who eats the same as the eight to ten hour fed mice, have similar muscle mass, runs only 75 minutes.


    That endurance advantage comes from when the mice actually eat for eight to ten hours. There are various reasons for that. One is, what we find is the heart function improves. There might be some ketone body production towards the end of the fasting period. In that way, time-restricted eating actually takes whatever fuel we eat. We are converting part of that fuel into ketone body towards the end of our fast and that's repairing or maybe improving function of our heart and muscle and that's giving this endurance benefit.

    Although we had seen that in mice in our -- we have ongoing study where anyone anywhere in the world can download this app, myCircadianClock and give us feedback and we do see there are a lot of people, endurance trainers that are training for endurance and they report similar outcome. If they eat enough calorie or whatever they're eating now for their regular training, if they squeeze that into eight to ten hours, actually ten is a good practical number because you shoot for ten and maybe you can squeeze slightly into nine, then they do see that extra benefit in the endurance.

    Of course, they will not run twice longer as the mice but at least 10%, 15% improvement in endurance. Those who are doing fixed length of endurance training -- For example, some people just stay on the spinning bike one and a half hours, then they are reporting that they are less exhausted at the end of that one and a half hour when they're on eight to ten hours. But if they go to 12 hours then they lose that advantage.

    This is something that we are very interested but, unfortunately, we don't have access to human clinic particularly exercise clinic. Hopefully, we can do this through some collaboration in the future in controlled condition.

Tommy:    If I summarize the things that you've said, I'm wondering if potentially you can manipulate food quality to get more calories in if you need to. Obviously, most of the time we focus on real whole foods, minimally processed, and I know that you recommend similar things in the book. But if you're somebody who is an athlete, has a high calorie requirement, but also wants to eat to a more restricted window, you may be have more scope to eat more calorie dense foods in order to get your total calories in but then you can still get the benefits of eating through a restricted window.

Satchin:    Yes. I totally agree with that. If this natural ketosis is one of the ways that endurance is improving maybe one can slightly -- I'm not advocating that everybody should do ketogenic diet but at least the precursors to ketone some good fat which also have a lot of calories. Hopefully, that will complement. In fact, in our mouse study, these mice that got extra endurance benefits are the ones who were getting 65% of their calories from fat. Of course, I don't recommend that for humans but it was surprising that only when they eat high fat diet with time-restricted eating that's very calorie dense diet we saw that benefit.

Tommy:    You, obviously, expected benefit from improving food quality as well as the timing because in your book you have a list of foods which are very much the kind of things that we would recommend, whole minimally processed foods, including fat. You're certainly not trying to restrict fat in people. You have healthy fat sources listed in there. Do you think, even if you're restricting your window to eight to ten hours, you'll see an additional benefit if you improve food quality as well?

Satchin:    Yes, of course. The time restricted eating is your foundation because whether you are eating healthy food -- if you are eating unhealthy food, which a lot of people are there to eat, then you reduce the adverse effect or bad effect of the unhealthy food by eating within eight to ten, maximum 12 hours, because you're giving your body enough time to detoxify a lot of the bad food.

    And then if you are eating healthy diet, eating that healthy food at the wrong time can make it unhealthy. So, timing can make a healthy food junk. Timing can increase your resilience against unhealthy food. Although you are improving your resilience against unhealthy food that's not the way to nurture your body. A simple example is, for example, if you're just eating high glycemic food within eight to ten hours, maybe during the fasting time your blood glucose level might be normal but in your eating period your blood glucose level might go through the roof.


    That's another example where you have to combine these two elements of food. In real life, what we see, although we tell people start doing ten-hour time-restricted eating we don't give them any practical advice on what and how much to eat. If they adopt a time-restricted eating window that ends somewhere between 4:00-5:00 p.m. to 7:00-8:00 p.m., during that interval, then they're less likely to drink too much alcohol, less likely to eat too much dessert.

    That will improve their nutrition quality. And if someone is previously eating for 16-17 hours and now going to ten hours or eight hours, of course, they reduce number of calories. And since they're hungry in the morning when they're eating their breakfast then they have a slightly bigger breakfast and they are more mindful about their breakfast so they tend to eat, improve the amount of protein and fat they have in their breakfast. They may even improve the quality of the carb. They might have more complex carbs and fiber.

    In reality, once people start doing time restricted eating, they most likely, in most cases, what we see is they also reduce slightly their calorie, the normal people not the trained athlete, and they may improve their nutrition quality.

Tommy:    What about the timing? You alluded to that slightly just now. It's very common for people who are trying to restrict their eating window. They may skip breakfast, start eating at 12:00 and then eat until 8:00 p.m., if they have an eight-hour eating window. How do you feel about that versus a breakfast and an earlier dinner? And then also what about the consistency of meals? Is it just the total window or is it when you are having those boluses and how regularly that's happening?

Satchin:    Yes. So, having the same schedule is very important because just imagine when you -- if you're having breakfast or your first meal every day around 8:00 a.m. and in the weekend you change it to noon, it's almost like four-hour time interval. It's almost like your body is going from one time zone to another time zone four hours away. You know how jet lag feels to the brain. The same thing will happen to metabolic system. Your metabolism will experience that jetlag. Having the consistency is very important.

    The second thing is when you should start. That's a tricky question because if you absolutely want to optimize everything, you want to be in 100% peak performance, et cetera, then there are some data that are suggesting that an early time-restricted is much better than late. But the definition of early and late doesn't relate to the actual timing of the day or night but it relates to what time you wake up.

    Because what time you wake up is your sunrise time because that's the time when you open your eyes and see light. It's not actually when sunrise is outside. If someone is waking up at 8 o'clock or getting out of bed at 8:00 then it's okay to have breakfast after 9:30 because for the first one to one and a half hour, as you know, cortisol levels, there is that peak within 45 minutes to an hour after we wake up.

    If someone is waking up to an alarm clock then the melatonin level might be still going down. In the first one hour your hormones are crisscrossing. Giving yourself that one to one and a half hour gap is pretty good. Then the question is which, ten hours or eight hours, you would choose? So, both. I'll say if eating any time is one goal post which is the worst one. Eating eight to ten hours starting from one and a half hour after waking up is another goal post which is the most optimum one.

    Then at late time-restricted eating is closer but would be identical to the early time-restricted eating but it's way, way much better than eating randomly any time. That's why I always say that try to figure out what fits you with your lifestyle. Because if you really want to have dinner with your family and the family is ready for dinner at 8 o'clock maybe that's what is most important and try to do that.

Tommy:    Creating something sustainable that allows you to still be connected with your family and do things -- that's a great point. That's very important. I know people will think about or ask about supplements. So, say, a multivitamin or something else that you would take on an empty stomach in the morning or before bed at night. Would you count that towards the window or is that something separate?


Satchin:    No, we don't count that towards the window because we don't know whether they affect our blood, how they affect our metabolism and whether it affects. Right now, we don't count anything medication, supplements, except if, for example, if you have gummy vites and you have ten gummy vites to get all of your supplements then you're taking ten spoons of sugar. That's one thing.

    People have very strong opinion about coffee. I always say if coffee is the last best thing in the world that you don't want to part with then it's okay. Have it without cream and sugar in the morning and try to avoid coffee after afternoon because that will interfere with your sleep quality. People said that, yes, I can drink coffee and still sleep. Of course, everybody who drinks coffee they can sleep at night. The question is, are you getting your optimal sleep?

    I drink coffee almost every day but right now, for the last one month, I stopped drinking coffee because I know that I'll get back all the lost sleep. I'm very sleep in the evening, a very deep sleep. In the morning I wake up very fresh. But still, some days, I have to stay awake for longer times. So, once in a while I have coffee.

Tommy:    Coffee for me would be the one -- if anything extends my window beyond that eight to ten hours it's probably my morning cup of coffee. I've certainly stopped drinking at late in the day. I used to drink it into the afternoon. And even now, sort of just restricting at first thing in the morning have certainly helped my sleep. I haven't been able to give it up entirely but maybe that's the next step.

Satchin:    No. It's difficult to give up.

Tommy:    That's a really good transition to talking about sleep versus the next sort of thing I need to ask you about. It covers to be podcast on its own but you dedicate a lot of the book to it because it's obviously so important. I wanted you to start by talking about some of the myths that you bust in the book. The first one is the myth of night owls and morning larks and then also the myth of biphasic sleep which people or some people say is how our ancestors slept.

Satchin:    There's this idea about night owl and morning lark and this is a simple experiment that, again, another researcher in the field whom I really respect because he does this very simple, very elegant experiment, Ken Wright, Jr. from Denver. Half of his lab people, there's a circadian rhythm lab, they claim that they were night owls and then the other half were normal people.

    He takes the lab for camping every year and then he noticed that when they go camping everybody goes to sleep around the same time and wakes up around the same time. There is no difference in night owl and morning lark. He measured melatonin level before bed time, before going camping and he could clearly see that there is a difference between night owls and morning lark.

    During camping, when they have no access to electrical lighting, whole day they were hiking, a lot of lights during day time and no light, it's only camp fire light, very dim light, everybody's melatonin rhythm normalized. They all began to rise at the same time early evening. And then in the morning almost all of them woke up around dawn, just before sunrise. This was really exciting for him because he realized that maybe half of us are more sensitive to light or maybe we have adopted more brighter light at home that's keeping us awake. When we go to a more natural setting where there is no bright light in the evening then these are the people who thought they are night owls, they will become normal.

    And independently have heard the same story from Michael Herf whom I also highly respect because he developed this app called f.lux that many people use. His entire home has only two lux applied in the evening. He has only spotlight and working lights to read and do any work. Once in a while he invites friends who claim that they are night owl, they cannot go to sleep before 2:00 a.m.

    They show up for dinner around 6 o'clock and then they have their dinner and then talk and by 9 o'clock these people are sleepy. We don't know what happened whenever we come to your home. We feel sleepy about 9:00. Maybe it's something in your food. He explains, no, it's not the food. It's the dim light. That's why a lot of people should pay attention to the amount of lighting that's in their house. Because right now we're all trying to change our lighting fixture with LED light bulbs and many of the LED is pretty bright and they can reduce melatonin level in the evening.


    We don't know why some people may be more sensitive than the other people. It's very important to pay attention to that. The second one is the biphasic sleep. This is where I think some historians have gone back to history and then found out a few instances of people reporting that they have biphasic sleep. People used to wake up around 3:00 or 4:00 in the morning and then stay awake for one to two hours and then went back to sleep.

    And it's true that in many cultures it was described. But at the same time there are sleep researchers who have gone to very remote parts of the world where there is no electricity and they have put these actigraphy devices to monitor when people sleep. And they don't see this biphasic sleep that widespread. So then the question is why there is this disconnect between historians finding examples of biphasic sleep and epidemiologists, more than epidemiologists, who are not finding.

    I think my answer is very simple. For example, if you start thinking about acid reflux or heartburn and you go back to history and look for the signs of acid reflux and different cultures in different parts of the world, of course, you will find examples almost every culture describing acid reflux. That does not make acid reflux healthy or normal. What is common in history may not be normal.

    At the same time if you go now cast a wide net and say, okay, let's see how many people in the US or say in some ancestral society now have acid reflux then you'll see, yeah, in the US one in three, one in four experiences acid reflux at least once in a year but in many ancestral populations where there is food is limited and then they eat before sunset you don't see that.

    I think this is where we have to ask what is the context in which it was seen and what are implications? Having said that, that is another component to biphasic sleep in modern world. That will lead to two things. One is as we get older our arousal threshold goes down. That means if there is simple disturbance in the room then we tend to wake up. The best example is the mother and the newborn baby sleeping together. The baby would sleep through the night and kick few times and then the mother will wake up every time but the baby will never wake up because the baby has high arousal threshold.

    As we get older, since we are more susceptible to waking up, then sometimes the bedding that we are sleeping on may warm up towards 3:00 or 4 o'clock in the morning because most of the modern bedding that uses foam will absorb some heat in the evening and then will reflect back around 3:00 or 4:00 in the morning and you wake up you feel like your body is hot and that's what happens with a lot of people. And once you wake up it's really hard to go back to sleep because your body needs to cool down to go to sleep.

    Then you walk around or maybe come out or roll to the other side of the bed, if there is no one sleeping there, and then you may fall asleep. That's what I think is the basis for biphasic sleep and you can completely address it. For example, a lot of people who do time-restricted eating, they report that their arousal -- they actually said that they go into deeper sleep. But in experiments in laboratory setting, what we are finding is, at least in animals, the arousal threshold goes up. They don't wake up due to these smaller disturbances.

Tommy:    And do you think that that's because there are fewer metabolic processes going on in terms of digesting food and all that kind of stuff because they've left a good period of time before they go into sleep?

Satchin:    Whatever I will say is my pure guestimate because that's a very interesting area that I would like to see more research because we don't know, for example, what is the neural basis for arousal threshold and what is the neural basis for sleep? We actually don't understand that. I can only say ideas if we have slow metabolism maybe or cold body temperature is low at least that we know will promote sleep.

Tommy:    Do you have any thoughts on exposing the eyes versus the skin to light and circadian rhythm? I'll give you the example of me. I use blue light blocking glasses at night. I turn all my screens off and if I do have to be looking at screen I use f.lux like you mentioned. And then when I go to sleep I put on a sleep mask so it's very dark in terms of what I'm exposing my eyes to.


    But there are a couple of lights in our bedroom. My wife sleeps less than I do so she may stay awake reading. I know there are some studies that suggest that light exposure on the skin could be enough to affect melatonin production. Is that something that I should be worrying about or do you think that just minimizing the exposure to light to the eyes is going to be enough?

Satchin:    I think as far as we know now that most of the light input to melatonin production is going through the eyes because there's one study in, I think, 2000 that showed that skin exposure might affect melatonin level but that paper has been disproved. As far as we know, state of the art as of now says that all light input that affect melatonin goes through the eye.

Tommy:    Great. That's the answer I was hoping for. So, other than the things that I've mentioned, is there anything else that you would recommend in terms of how people improve their sleep, maybe a period of time after the last meal before they try and go to sleep? Anything else that they can use, sort of simple low hanging fruit they can use to improve their sleep?

Satchin:    I think I already mentioned two things, no light in your bedroom and two to three hours before going to bed avoiding light, no food two to three hours before going to bed. All of those will improve sleep.

Tommy:    What about naps? You mentioned benefit of naps in terms of reducing sleep, if necessary, but are there times when you would say yes or no to recommending naps for people?

Satchin:    Yeah, naps, particularly when you're trying to beat jet lag or if you are a shift worker you are going back and forth between two different shifts, that's where naps become very important to pay attention to. Supposedly you have jet lag. If you nap in the afternoon then you are more likely to stay awake in the night. So, if you register temptation to nap in the afternoon then you are more likely to get to deep better night sleep.

    Same thing for shift workers. We see some shift workers have mastered the art of napping in a way that they use nap very judiciously and to shift from night shift to day shift during when they have to mingle with people, have their normal social life. This will entirely depend on which kind of shift you are in and what you are doing. But coming back to other forms of nap, for example, if you are sleep deprived during the week, weekdays, and in the weekend you are trying to catch up as much sleep you want, and if you think that napping will not affect your nightly sleep, go nap because you should get as much sleep as your body wants.

Tommy:    And do you have any other tips for, I guess, two specific groups of people, might be night workers or people who consistently work at night, in terms or timing their meals, timing their light exposure, but then also people who work swing shifts. I remember when I was working in the emergency room I worked three or four night shifts in a row then I get a day off and then I'd be back to day shift. Is there any way to minimize the effects on your circadian rhythm in terms of light exposure, sleep, food timing, all that kind of stuff?

Satchin:    Yeah. This is a very challenging area. As you know, there are 10,000 flavors of shift work. The simplest one is 24-hour shift. That's where we are studying San Diego firefighters. One thing that has become very clear only very recently is studies showing that when in animals are given shift work paradigm, moving their food timing is much more effective in resetting their clock than changing the light timing alone.

    I think this is a very exciting area because people who are going back and forth between day shift and night shift, if they time their food accordingly and move their food timing with the shift work then that might benefit. I strongly say this might because there is no study yet and it entirely depends on what kind of shift work you are doing and what is your shift work environment.

    Because, for example, a nurse working in ICU may not have opportunity to eat at work whereas someone who is doing a different kind of shift where he or she can bring food to work will have opportunity to eat. That's why I said shift work is very complicated. At least we're starting with very simple 24-hour shift with firefighters and emergency responders who do 24 hours.

Tommy:    It will be exciting to see what comes out of that. I guess, similarly, moving across time zones. So, I guess, for myself, lots of people listening to this, lots of athletes we work with who train and race in multiple time zones, they'll travel frequently, in terms of adjusting more rapidly, do you have tips, again light exposure, food timing? Would you change that before you travel? Might you use exogenous melatonin or change your light exposure? Anything like that that you've seen benefit from or people might get benefit from?


Satchin:    Right now what we are seeing is a lot of people in our study who self-reported said that at least changing the food time has the biggest impact in re-entraining. It actually boils down to very simple thing. For example, most of the flights from US to Europe, they leave in the afternoon or even from US. They reach in Europe early morning. And the flights are short, six to maximum eight to nine hours.

    In those nine hours in flight, the only thing you can do is try to close your eyes and sleep as much as you can because you are reaching in the morning and as soon as you get out of the flight it's better to expose yourself to light. If you have fasted for 12 hours, that's nine hours in flight and then maybe two to three hours before check-in, leaving your home, et cetera, there's a very good chance you can nicely re-entrain because you are getting your light, you are getting your breakfast. Both your brain clock and [0:46:09] [Indiscernible] clocks maybe entrained.

    That's for a lot of flights from US to Europe. Coming back, European flights usually leave between 10:00 a.m. and 2:00 p.m. from Europe. It reaches US I think in the morning.

Tommy:    It's almost a similar time. The length of the flight is almost as many times as you're going back, or at least frequently.

Satchin:    Again, if you think about it, there is not much scope. You just have to -- Actually, coming back, maybe you can watch a TV show or something because you are reaching the day time, you left in the day time, but at the same time you are depriving yourself. Coming back is slightly little bit tricky.

    But the bottom line is, what I tend to say is try not to test the in flight food. Don't watch TV because there is not much time. You have to give yourself that rest. And only when you go more than ten time zones, flying between Boston and Melbourne or Singapore, between Beijing and East Coast, that's when maybe you can have one meal in flight. But give yourself at least 12 hours fasting before you have your next meal in the new time zone. That seems to work the best.

Tommy:    That sounds like good and simple advice which I like. Then the next thing, which you obviously mentioned frequently in the book is physical activity, any form of physical activity. You mentioned actually some potential benefits from both exercising in the morning and exercising in the afternoon. Do you have a preference or do you think it's just more important to do it whenever it's convenient to you?

Satchin:    I think whenever it's convenient is the best thing because our schedule is so tight. Moving anything in there is not easy. The morning exercise, as I said, has a lot of benefits particularly morning exercise, some kind of endurance training outdoor. And as you know, training low has a lot of benefit. Training low means training in low glycogen state, has much better benefit on the mitochondria. But, of course, you cannot sustain it and you cannot train low for competitive sports.

    In the morning, exercise has that benefit. Afternoon exercise, we have built for, we have been optimized for afternoon exercise and physical activity. And people always ask me what about middle of the day exercise? And it has a very different benefit that I didn't talk about in the book, that is you might -- a lot of people might have noticed that once we get into the office and we start working, what I call email-apnea, that is when we are checking out emails and going through different things we forget to breathe.

    And half of the tiredness in the afternoon is email-apnea because we forget to breathe. So, mid-afternoon exercise will actually help you to breathe because you're going to aerobic exercise and you regain the oxygen, you try to breathe. It's a very different kind of benefit.

Tommy:    Okay, that makes sense. I guess, if we're trying to apply all these principles, one of the reasons why people might be interested in that is either preventing or reversing some kind of chronic disease. We talked about metabolic disease, type II diabetes, a little bit we talked about obesity. What about something like cancer? Can you talk about how circadian rhythm disruption might lead to cancer and how we should focus on circadian rhythm that might help us during cancer treatment?

Satchin:    It has a very long history. Three things. One is prevention of cancer.


    There is now a lot more epidemiological data showing that people who eat all their meals earlier in the day, when I say earlier it's a Spanish study that came out. For them early means eating your dinner before 9:00 p.m. Spanish time. And they have 20 papers on less risk breast cancer and I think prostate cancer. Those are the two cancers they have looked at.

    In the US, there's also another study showing that women who fast for 13 hours overnight have less breast cancer risk. There is now accumulating evidence that having a strong circadian rhythm, mostly eating fasting seems to have much better benefit in prevention. Conversely, there is also data that women who do shift works are at very high risk for cancer. That's why shift work has been categorized as a potential carcinogen.

    Then during treatment there is also data that different drugs have optimal timing of efficacy. So, many breast cancer drugs when given in the morning or afternoon, depending on the drug, has a peak efficacy, and that I described in the book. Then one thing is the adverse side effect. That's, I think, is an emerging area because we know that a lot of chemotherapy drugs have a lot of adverse side effect not only during chemo, post chemo, and some of the side effects can continue so that's an area, emerging area where people are trying to figure out how to combine time-restricted eating, optimal drug timing, et cetera with long term outcomes among cancer survivors.

Tommy:     And when you are talking about circadian rhythm disruption and you, obviously, present evidence in the book, that it could contribute to pretty much any modern chronic disease, any kind of circadian rhythm disruption seems to affect our risk of those, is there anything else that you think is important? We talked about time-restricted eating, proper sleep, obviously, physical activity. Is there anything else that you would put on your list of things that we should maybe be thinking about in terms of minimizing long term risk of chronic disease?

Satchin:    When I say lifestyle, lifestyle is what, when and how much. We eat, sleep and move on a daily basis. Although I speak a lot about when aspect, the timing aspect, let's not forget what and how much. So, when it comes to food, what and how much you eat, when it comes to sleep, what type of sleep, how much we sleep. That also matters. And then physical activity is also very important because depending on your age and your physical fitness, what and how much, what type of physical activity and how much physical activity is optimal for you are also important.

    These nine elements really constitute lifestyle. Actually, there are three more elements that I did not touch upon, that's what and how much we eat, sleep, move and connect. Our connection with ourselves, connection with the society, that also matters for our mental health. This is something we also have to keep in mind that we are social animals and we have to be mindful of other interaction. We have to have friends. We have to have happy times.

Tommy:    Yeah, absolutely. That's very important. The last bit then on how much or what we eat, I have some questions about your work with Valter Longo who I know you've done some research with. He's mentioned in acknowledgments in your book. He has just written a book where he promotes calorie restricted and quite low protein diet for longevity. That's his focus.

    My personal bias would be that if you improve diet quality and then you had a well timed feeding window, that would be more important than actually restricting calories. I think that might be more in line with your work. I was wondering if you had any thoughts on the differences between your recommendations. Because the two of you are probably right at the top of anti-aging and health research in terms of diet and other factors.

Satchin:    Yeah. I mean, what Valter has been doing is really culmination of almost close to 100 years of research in calorie restriction field where people have really honed in to the molecular mechanism, et cetera. There is no doubt that low calorie diet, at least for a few days, has lot of benefits. The way I look at this too is if time-restricted or keeping a fixed schedule eating is like brushing your teeth to take care of your teeth then once in a while you still have to go to the dentist and get some deep cleansing. That's where this occasional five-day fast with low protein diet like Valter Longo is advocating might fit in.


    In this way, these two are complementary. It's almost like taking care of your teeth. You got to brush your teeth. If you don't brush, of course, you may have to end up in dentist office too often and you may not like it.

Tommy:    Well, I'm British, obviously, and we're known around the world for our very infrequent visits to the dentist and maybe that's part of my resistance. I know that makes a lot of sense. I think we should potentially integrate them without thinking that they're sort of antagonistic approaches.

    Moving away from the dietary stuff, I wanted to briefly ask you about the work you've been doing looking at architecture and how to increase light exposure to improve health and productivity in people and the buildings they're working in. You mentioned a study in the book that you did with some employees before and after they changed building. Can you talk a little bit about the work that you're doing in terms of that?

Satchin:    Yes. Architecture means this is a very challenging study because what happens is even though you build a nice building where there's a lot of light coming in and people are happy, sometimes you cannot do post-occupancy survey because imagine if there is a large corporation that has 10,000 people in 50 different buildings and they can afford to change only one building, it's a very healthy building that bring these thousand people into new building and they found out that these people are really healthy, they're much better now, then it's a liability. Because the other 9,000 employees will now complain.

    That's the biggest roadblock that we have to show that, yes, this is good. But at the same time now there are parallel studies, a lot of other people who have started this and they're finding that having a good building that brings in a lot of natural light during day time can reduce your energy cost from lighting, also improve people's alertness and reduce sleepiness.

    No one has looked at long term depression because that's again you are getting into liability territory. But that's an area where the conversation is just beginning. This is where the building architecture, the lighting designers and building guidelines, those things are coming together. There is no real guideline for health now in building in terms of circadian health.

    What we are going to see in the next five to ten years is new guidelines will be laid out and people will pay attention to that. The smarter buildings will have, will support circadian rhythm very well. It all goes back to one simple thing, that is, for thousands of years we live in a natural environment with strong light-dark cycle and we created the man-made wall only in the last 150 years.

    And we haven't incorporated the principle of this light-dark cycle into our built environment. So, that's why I said that the science of circadian rhythm will have huge implication in many areas of our life not only eating, sleeping, exercise but what kind of building we live in, what time our high school start time would be, and how we should schedule shift work, when we should serve meal in trans-Atlantic long haul flight, and what type of lighting should be even in trains, commuter trains in night time versus day time or in long haul flights.

    So, what we are seeing is just the very, very primordial beginning of a completely new world where we will incorporate the principle of circadian rhythm into almost every aspect of living.

Tommy:    Yeah, absolutely. It actually just made me think of, I think it's the new Boeing Dreamliner where they have all the mood lighting but it's a nice bright blue color that they have throughout the night as you're flying trans-Atlantically. It's a perfect wavelength to disrupt any attempt to re-train to your new place. That's actually one thing we didn't' talk about too much was we talked about the importance of darkness, but the importance of light and the brightness of light and when we're exposed to that. Maybe you could briefly talk about that. I know you have an app too that people can use to help monitor or make sure they're getting adequate light exposure.

Satchin:    The rule of thumb now is get at least 30 minutes of bright light. When I say bright light, at least 1000 lux. And even if you don't have a lux meter, the rule of thumb is even in a cloudy day in London of Seattle outside you get 10,000 lux of light. If you're sitting right next to a window looking outside to a cloudy day you are still getting close to 1000 lux of light. Trying to get that 1000 lux of light for half an hour in the morning is very good.


    If you can't do that then at least consider having bright light installed in your room. Most of the bright LED these days, if you have to two or three LEDs in a standard office room then that will give you that kind of light. And also if you have a large laptop or desktop monitor at the bright setting you'll also get a good amount of light. At night time, if it's just dimmed down that's the best way to entrain your circadian clock.

Tommy:    Well, I think that's probably the perfect place to start wrapping up, very simple actionable and important advice. I would very much like people to read your book and find out more about your work. Maybe you can tell us the best ways to do that.

Satchin:    Yeah. So, the simple advice that we typically give to our patients in our clinical trial is try to be in bed for eight hours at least, and then after waking up give yourself one and a half hour before you think about eating anything or drinking anything, and then try to eat all your food within ten hours. That's a good practical goal. If you slip down to 12 hours, that's still good enough.

    During day time, try to get at least 30 minutes of bright light and the best way to do that is to do some workout outdoor, running, walking, then you get both physical activity and light. Three hours before going to bed, no food, dim light, and prepare yourself to sleep. I think these things will help a long way.

    If you want to participate and share data with us for a scientific study then go to to sign up and get the activation code for the app. The book is available from any major internet book sites, Amazon, Barnes and Noble, et cetera. And we'll soon release the IOS version of the light measuring app that will be called myLuxRecorder. It's now available only in iOS. You don't have to do any informed consent. It's a cool toy to go around and measure how much light you have.

Tommy:    Great. Absolutely encourage everybody to go and check all those things out or participate in research and check their light exposure. Thank you so much, Satchin. This has been brilliant. I'm really appreciative of your time.

Satchin:    Thank you, Tommy.

[1:02:36]    End of Audio

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