Leading Circadian Rhythm Expert Dr. Satchin Panda Shares 6 Secrets to Longevity

My guest today is Professor Satchin Panda, a world-renowned circadian rhythm researcher and leading authority in the field of chronobiology. You might also know the concept of time-restricted eating, aka intermittent fasting, work that came out of his lab. With a passion for understanding the impact of our internal clocks on health and well-being, Dr. Panda has dedicated his career to unraveling the intricate relationship between circadian rhythms Sleep and overall human physiology. Through his groundbreaking research, he has shed light on the effects of disrupted sleep-wake cycles and artificial light on our health, offering practical strategies to optimize our daily routines. He is a professor at the Salk Institute and founding executive member of the Center for Circadian Biology at the University of California, San Diego. Please enjoy our talk today on optimizing your health and longevity using circadian rhythms. Welcome to the Longevity and Lifestyle Podcast. Professor Dr. Sachin, such a pleasure to have you on today.

Yeah, happy to be with you on this podcast.

So I'm very excited to have you on. Obviously, I've been following your work for several years and being in this space, and I heard you present last year at the Health Optimisation Summit in London. But I really wanted, and I'm delighted that we could make this, this time to really bring the concepts of your work and what it's doing and the implication, because it is just so important for every single person to understand better out to the world. So let's start with the concept. As you are the, the world leader in circadian rhythm, can you explain exactly what the circadian rhythm is and why is it so important for our health and well-being?

Yeah, so the word circadian actually literally means near 24 hours. So that means anything that we experience or our body goes through once in every 24 hours is considered as circadian rhythms. And we always think of, we're always told that, well, our DNA holds the blueprint for our bodies, just like any blueprint for a building, the DNA codes everything. But what we forget is when we build the building, whether it's an office building or it's a school, it's not a dry building. It actually has life into it. So something happens during the day, something happens at night. And you look at any building that has specific tasks happening at specific time of the day. So for example, before the office starts, the custodian staff would come in and clean up the place. And then the cafeteria people, and then they will come and brew the coffee. And then people will show up. And the shipping and receiving would come. So similarly, what happens is in our body, our body is not static. And we know that what I am in the middle of the day and who I am in the middle of the night are very different. So the basic concept is just under this seemingly sleep-wake cycle, our body actually goes through a huge number of changes between day and night. And if we think of every hormone, every brain chemical, every immune response or immune modulator, every enzyme, digestive or anything else, even every single gene turns on and off at specific time of the day or night so that Then the question is, why are these rhythms? These rhythms essentially do a few things. One is they consolidate similar tasks. Like, for example, when you are awake, which our muscle tone should be better so that we go running. Just imagine if your muscle tone is much better in the middle of the night, then you would be acting up on your dreams and you'll be kicking and screaming.

Kicking around the place.

Yes. So, and then the second is separating incompatible process. Same thing, as I said, your muscle tone should be compatible with the daytime, not with nighttime. Similarly, our bowel movement should be in the first half of the day after we wake up and clean up our bowel so that we are ready for food. So even at a very complex level like genes and proteins, we do see these things. And then the third one is anticipation. So for example, in anticipating waking up, your heart rate begins to increase, your body temperature begins to rise up slightly. So it prepares our body for the next act in the day. And if you're not prepared, just imagine if you're not prepared for your exam, if you're not prepared to go to the doctor's office. So circadian rhythms prepare all of this. So then the bigger question for everybody is, so what? Why should we pay attention to it? And this is so what thing actually relates to why we cannot live a long, healthy life. I mean, if we're designed to have this DNA to give us this perfect body and mind, then why we cannot live? The reason why we can't live a long, healthy life relates to 4 major types of disease. First one is infectious disease. Everybody can relate because we all came out of COVID but there are many more infectious diseases that make us sick. And second is the metabolic disease— obesity, diabetes, starting from there to cancer, all of these. Affecting millions and billions of people these days. And almost 1 in 2 adults in the US or in the Western country is going to experience at least diabetes. 1 in 2 is going to experience high blood pressure. 4 out of 10 will be diagnosed with cancer. All of these bad things are going to happen. Then the third one is brain health. The statistics is very different because at any given time, 5 to 15% people may be experiencing depression anxiety. But in our lifetime, if you take the entire lifetime, 85% of us will experience or have experienced some kind of depression, anxiety, which is clinically significant, clinical depression, anxiety, or PTSD. And then the fourth category that I say is injuries. We know that, for example, I just crossed 50 a couple of years ago. And the reason why I cannot run as fast as I could or I want to, or why I cannot lift certain things, is because I have certain injuries. And as we get older, we accumulate injuries, and that also reduces our performance. So getting injured and coming back to full play is what we need. So what is interesting is over the last 20, 25 years, scientists all over the world, there are very few scientists who actually work on circadian rhythm, but they're really smart scientists. And we figured out that circadian rhythm actually optimizes our health so that our body can better fight infectious disease. And second, it can actually, if we have good strong circadian rhythms, this day-night cycle, then we are also more likely to prevent chronic disease from diabetes, obesity, all the way to cancer, even dementia. We can even combine the principle of circadian rhythm with whatever treatment you are doing right now to accelerate cure and come back to full play. And similarly, it's becoming very clear that certain principles of circadian rhythm, for example, sleep, Maintaining proper sleep-wake cycle, maintaining enough light exposure during daytime, avoiding light at night, and combining that with proper timing of nutrition, etc., can also reduce the severity of depression, anxiety, and improve brain health, improve mental performance. And just recently, we are beginning to understand that many of the injuries and prevention of injury and then coming back to full play, whether it's bone injury, whether it's muscle injury, all of these injuries, having a strong circadian rhythm also helps us to better repair ourselves. And having a strong circadian rhythm and having physical activity at the optimum time also prevents injury. So that's why I'm looking at almost every health concerns for everyone through the lens of circadian rhythm. The reason is this is such a powerful concept and it doesn't cost anything to adopt this into our life. Of course, you can spend a little bit money to optimize your circadian rhythm, but this is something that we can— the solution is now, it's right now. And if we just understand how these rhythms are regulated or how we are the master conductor of these rhythms through when we eat, when we fast, when we sleep, when we wake up, when we get exposure to light, and when we exercise, few simple things, then we can actually leverage the power of the circadian rhythm. And I'll give you some specific examples where this simple attention to circadian rhythm is even more powerful than the best medication available.

Um, yeah, and I'd love to hear those. And what you just said is just so powerful, that not only can it help to optimize, but it can reverse so many of these, um, chronic diseases that are affecting so many people. Um, and everyone, I think, has some connection to one. My mother has dementia, my father has cancer, relatives have issues. Um, and, you know, the beauty is, is that when you've understood this model— and I'd love to hear some use cases as well that you've seen some transformations. Um, but I'd love to break it down, how does one master the rhythms, as you were saying? How does one, A, understand if they're off balance, and B, what is the right time for the individual? Because we are all different.

Yeah, I guess you are asking a very fundamental question. What are these rhythms and how our lifestyle or what we do affect these rhythms? So it all boils down to one fundamental reason why we have these rhythms. For the last 200,000 years, we humans have been living on this planet, and for almost a billion years, other life forms are on this planet. And over the last billion years, you may argue, okay, so there was global warming, there was global cooling and all that stuff, but— and seasonal changes. But there's only one constant through that billion years, that is, sun came up and went down, and then exactly approximately after 24 hours, the sun came up again. So it's a very powerful cycle of light and darkness. And with light and darkness came warmer temperature and cooler temperature at night and also access to food for day active animals like us, access to food during day and mostly fasting at night. And then for people, for Animals and humans who are day active, they have to run back at the end of the day to go to safe places to hide or run home. So these very fundamental rhythms in getting exposed to light during the minimal light or darkness at night, that's one rhythm. Second, eating mostly during our wakeful hours during the day, because in the old days there was no processed food and preservation, and maintaining an overnight fast at night, then having all this lot of physical activity towards the end of the day. Those were the only constant that actually happened for the last 200,000 years for humans. So as a result, our genome, our physiology, our metabolism, our brain function, everything is tuned to this cycle. And just imagine, we cannot live outside this modern world for a few days. Imagine if we— I cannot imagine if you drop me in the middle of some wilderness where there is no modern amenities. I cannot survive there. Yeah, I cannot survive there for even more than a week or month. And just imagine our ancestors, they live up to, say, 20, 25, 40, sometimes 40, 45 years. Because they built up that resilience against disease, against injuries, against all the metabolic disease that we are talking about. And also they have to be alert. They cannot be depressed. The lion will come and kill them. So, so all these things were there. So now the question is, you cannot go back to that ancestral life because our modern life, our modern way of living involves— actually forces us to be active at night, to be more exposed to light at night, and we have access to food all the time, and we are sedentary. So now the question is, we can't give up the life of the modern world, and creating wealth goes synonymous with breaking our circadian rhythm. You cannot expect to make a lot of money and be rich or bring enough for your living to pay for your family by just going to bed at 7 o'clock in the evening and waking up at 4 o'clock.

Unless you get up at 4 AM, maybe. Yeah.

So the point is, how do we manage this? And then who is getting disrupted? And how do you understand that you are disrupted? So let's begin with a very simple thing. Like, if you're sleeping less than 7 hours, you already have a problem with circadian rhythm disruption. So many of us can relate that if you sleep for kids, for toddlers, for young adults, it's even 9 to 10 hours. Those of you who have a kid, you know that the night the kid did not sleep for more than 8 or 9 hours, the next day you will know that there was a circadian rhythm disruption. So that's very simple that when we don't sleep enough, we have immediate sign that something went wrong. Because when we sleep, that's when the combined action of sleep and circadian rhythm, they help detoxify our brain, literally detoxify, because many of the toxins, many of the breakdown products, byproducts that are not necessary for our brain, are actually drained out during our sleep. Second thing that happens is during sleep, our brain cells or neurons, they strengthen connection between them. And then the question is why this is important. When our brain cells talk to each other and strengthen connection, then our brain can take in information correctly, process it correctly, and also spit out the reaction correctly. So the reason why the kid becomes cranky is cannot process the information coming in correctly or cannot process the information that's given. And instead of smiling, starts acting out. And the same thing happens to all of us. And in fact, if we go back to a very simple thing that almost every adult experiences, that is conflict between couples, between loved ones, If you think carefully, you'll often find that at least one of the partners either did not sleep enough, have been traveling a lot. And so it affects not only your brain health, it actually affects even your family. So that's one.

Note to anyone listening with relationship issues, just note if you or your partner have slept enough, and if not, maybe park it until you're both well-rested. So Scientific proof.

So my rule of thumb is I never argue with my wife after 11 PM at night because I know that this is the time when my brain is loaded with toxins, has not drained it, and I'll be making emotional— when we say emotional, what does it mean? It means irrational because my brain is not processing information. So we kind of have a wonderful rule that, okay, that's not an argument.

Pick a better time.

Exactly. And we also know that if we haven't slept enough, if I'm coming back after long travel and all that stuff, I'm also irritable because— so this is a very telltale sign that you want to see whether you are a circadian rhythm disruption. So this is one. Second is, and these days we have a lot of light. And when you're exposed to a lot of light in the evening hours, So we have two problems. One is too much light in the evening. So a lot of light in the evening. And these days, even we go out and buy those very brightly lit LED lights because we want to feel more, a lot in the evening, because everybody is coming back home very tired. And they just— but still, after coming home, we have to enjoy the evening. Time, because the life after sunset is very different from the life before sunset. Life before sunset or life before evening is all about— for an average person who is doing a day job, is all about working, making enough earning so that the person can enjoy. And life after evening is very different. We want to socialize, we want to share our thoughts, we want to entertain ourselves, we want to care for each other. We're going to share a meal and we want to feel energized to do that. And then we turn on all the lights to be energized to do all of this or watch TV. And then the problem is that bright light can suppress many nightly hormones, including melatonin that actually helps us to sleep. So, and that way we have another circadian rhythm disruption if you see that you cannot easily fall asleep even though you're tired. Your hormones, your melatonin is not high enough. It's not telling your brain that, hey, it's time to sleep. Rather than it's actually telling you may be tired, it's okay, but I don't see any sign that night has arrived and you can sleep. So that conflict happens. So there are a lot of people that say, I'm tired, but I cannot sleep. That's another sign that your circadian rhythm disruption has happened.

Can I ask a question around that? Sorry to interrupt, because you've done work around blue light and how it affects in the retina, and I'd love to just dig into that for people to understand exactly. And the differences also between that blue light, junk light, and then like more warmer tone light. Like, is there an implication or a big contrast between them? Like, is there a good light versus the blue light, which we know is the junk light. But can you just break down the science a little bit, like what's happening that the light is affecting melatonin production?

Yeah, so this is where I would also bring up another thing, that light is not good or junk, it's the mistiming of light makes it good or bad.

Okay.

So people always say blue light is junk light, like you said, but it's actually The evening excessive blue light is what disrupts our circadian rhythm. So coming back to— it's good that you pointed out this very important discovery from 22 years ago. Let's step back and then talk about light. So if we think carefully, if you're not living right at the equator, for example, you are in London, and if you look up now your sunrise and sunset time, you'll see that the sunrise to sunrise time is not exactly 24 hours because of the tilt of the planet, of our planet and the rotation. So that's why it's not exactly 24 hours. So that means every day our circadian rhythm or sleep-wake cycle, if you're not exposed, means in the modern world it's different though. But our ancestors, they had to adjust their circadian rhythm every single day because it's not 24 hours, the sun depending on whether it's summer to winter or winter to summer transition, either the sun comes up slightly later or earlier. So then how does this sunlight or daylight signal get into our clock? And for almost 75 years, starting from 1920s, scientists knew that all the light information to our clock circadian clock goes exclusively through the retina, at least for humans and mice, not for birds and other animals, for humans and mice and rats, all light information that is required to reset our sleep-wake cycle clock or circadian rhythm clock goes through retina. But here is a twist: there are many animals and there are many humans who are blind because of some genetic disease or something happened, they, or due to age, they are blind, they cannot see anything, they cannot read anything, and everything is dark for them. But still, they could reset their circadian rhythm just like normal people. And there was this conundrum, you need the eye. Why people knew that they need the eye? Because there are many, many people who went to war, they lost both the eyes, or they had cancer in both the eyes, the eyes were completely removed, and they could not reset their clock to this day-night cycle, so they would drift. So then in 2001, 3 different labs, including, I was the first author in that paper, we discovered that there is a blue light sensing protein called melanopsin. And this melanopsin protein senses blue spectrum of light. And you might say, well, I don't see any blue light, but we all know that this daylight has all these 7 colors, so that's why we have the rainbow colors. So So daylight is actually the richest source of blue light. There is nothing else, there is nothing that we have designed so far that, or any other light source that can exceed what the daylight or sunlight can produce in terms of blue light. So this blue light sensing protein senses daylight, sunlight, and used to reset our clock every morning. And in the evening, all our ancestors lighted up some fire and grilled something or baked something, whatever they did, there was some light coming out of this ember or fire. That firelight was mostly orange color because there is not much blue light there. And this melanopsin protein was not sensitive to blue light. Sorry, to orange light. So that's why even though there was orange light, even though people could actually see each other, sing and dance, or talk stories to each other, that light was not very effective. And as a result, by 9 or 10 o'clock, these people would get tired and go to sleep. And in fact, even these days, some of my very heroic scientific colleagues who have traveled to very few parts of the world where there is no electricity now. You can imagine that it's not easy to access those places. They go there and then study people who have no access to light, electrical lighting. They have firelight. And they literally, they switch flips between 9:30 and 10 o'clock, all of them would go to sleep. And then exactly at dawn, when there is twilight, they all wake up just like there is an alarm clock went all over the village. They all wake up and become active. So that used to happen. So now with the new bright LED light that we have indoor, these LED light, particularly the white-blue enriched LED, if you have any confusion, just walk to any grocery store or drugstore, anywhere in the world, they're all blue and red LEDs.

It's not a very flattering light either.

Yes. And that's the light that you want to avoid because of course in business, for example, you don't want the pharmacist in a pharmacy to fall asleep and make a mistake. So that's why it's okay to have that bright light in pharmacies and drugstores. Same thing when you go to Grocery store, two things happen. They want you to be awake and grab as many items as possible. It's good for business and also the checkout. So the point is you don't need that kind of light in your bedroom, in your living room. So that's why you have to pay attention. And the good news is there are two solutions. One is instead of light switches, you can install dimmers, light dimmers, so that you can dim down the light irrespective of what light you have. You can just dim them down because another property of this melanopsin protein or melanopsin blue light sensing sensor is it cannot actually sense too much of dim light. What is dim light? For example, if you're old school, if you had access to a 40-watt light bulb, an equivalent will be a 40-watt equivalent LED light. And if that light is kind of and the ceiling in a big room, say, 3 meters by 3 meters or 12 feet by 12, yeah, something like that, 10 feet by 10 feet, something like that. So then, that 40-watt light bulb in that kind of room will give you what is considered dim enough light so that it don't activate your melanopsin as much as. But there is a caveat. But if you're sitting in there and then you have your eye If you have your tablet or PC or laptop with full glare, that will also disrupt your circadian rhythm. So that's why it becomes important to kind of pay attention to lighting. So rule number 1, don't put too much LED, blue LED light in your living room or bedroom. And if you do, because I'll tell you why you should sometimes, then instead of flipping light switch, the old style light switch, put a dimmer so that in the evening you can actually dim them down. Or if you have more money, you can actually have a programmable timer that will dim down the light. So that's about control, purchasing the light and controlling it. Second is we get a lot of light exposure from rectangular pieces of glowing objects, whether it's your phone, whether it's your laptop, whether it's your tablet. And fortunately, all of them have inbuilt feature to what is called night shift feature. So you can turn that on. So depending on what is your preference, maybe 8 o'clock or 9 o'clock, they will all dim down or change their spectra to orange color light. So that's half of the story of how you should manage light in the evening. During daytime, the story is very different because For most of us, we spend most of our time in dimly lit classrooms for high school, college students, or in offices. You know, only when you are a top-notch executive, you'll get that corner office or access to large window. But for most people, they're actually stuck in an interior office with very little access to windows. And even though you have a bright light, you think it's bright enough, that light in most cases is not bright enough to fully activate your melanopsin or blue light sensor during daytime so that you feel more alert. You can actually take more, you are happier. So that's why during daytime you need to be exposed to at least 30 minutes of daylight. When I say daylight, you don't have to go out and look for the sun and stare at sun. Even in London on a cloudy day, you get sufficient, you get 5,000 to 10,000 lux of light. And 5,000 to 10,000 lux is a hell of a lot more because in the evening, if you walk into a drugstore or grocery store, you are getting only 1,000 lux of light. So a cloudy day in London is at least 5 to 10 times brighter than your bright drugstore that you can work in.

Yeah. If it's cloudy though, do you need to increase the time? So say it's a sunny day, you want to aim for— is it just 30 minutes a day to get that exposure? And then ideally in the morning, would you say? Or if it's cloudy, does it need to be an hour or 2 hours to be equivalent?

It kind of reaches saturation around, um, 4,000 to 5,000 lux, so it doesn't matter. But okay. What we feel is there is some more benefit of even super bright light. Like, for example, a daylight with full sun in London will be 100,000 to 200,000 lux. Wow. And we know that there are now— there are also infrared light coming, and then there is UV light, so we have to be careful about. But there are also new violet light sensors. There are many new light sensors that are being discovered these days. Which suggests that there are other functions of light that may be going through your skin and not directly related to circadian rhythm but for other reasons. Like, for example, vitamin D. If you want to avoid taking a vitamin D3 pill, then, of course, you have to be exposed to more light. But when it comes to just regular people who are not depressed and they want to get some enough light, the morning light is better because our executive function is much better in the first half of the day. We're already programmed to be more happier a lot and have ability to take on complex tasks. And on top of that, if you actually get this blue light spike, then that helps to have that high performance for the first half of the day. When it comes to people who are feeling low, depressed, whether they're on medication or not, it doesn't matter. Any bright light during the day is extremely important for their brain health. And this is something that we always have to keep in mind. Means we always say that, well, there are so many kids who are these days going through depression, almost one in, depending on the stats, how you look at it, one in three college-going female students and one in four college-going male students may be experiencing depression. And we talk about a lot of things about social support and other stuff. We never talk about one thing. Are their dorms lighted enough? Are they spending too much time in front of the computer so that they're actually not going outdoors? So when the issue of mental health comes in, I always tell if you want to care for somebody, just take them out for a walk in a— during the day. It doesn't matter whether there is bright light, dim light, cloudy day or whatever. Just take them out for a walk. They will get your company, they will get some physical activity, and they'll get light. And light is the best— daylight is the best antidepressant. It's plentiful and free. You just have to step outside. But when you're depressed, you may not feel the urge to go outside. And that's why your best service for somebody you care for who is depressed is to take them out for a walk. During the day. So this is a story about more light during the day. And for depression, most researchers agree that you have to get that daylight for at least an hour. 30 minutes may not cut it, an hour is better. And if you cannot go out, then at least if you're living with someone who is going through depression or feeling low, at least open all the curtains in the room And if you have even extra light, as I said, LED light, this is where the LED light or the bright light comes into play. They should be in a brightly lit room with large windows and a lot of light should be coming in, and that will help a lot.

That's powerful advice, especially coming out of the pandemic and obviously where people were spending a lot of time indoors. And I remember reading research that the average American and the average UK citizen spends up to 90% of their days indoors. So already there, that's just getting outside more often, ideally moving, ideally in nature if possible, will just totally shift so many different balances and support the circadian rhythm as well. So that's really great advice. Thank you for sharing that. Regarding sleep, you were saying timing is so important. So there's the quantity, But then the question is, some people are like, well, I'm a night owl. I work really well in the evening, or I wake up at 4:00 AM. Like, people have different rhythms, if you will. So how does one understand circadian rhythms when there's a couple, one goes to bed early, one goes to bed late, and they sort of function that way? Like, how can one think about optimizing circadian rhythms for sleep with different sleep schedules?

Yeah. So here's a tricky question because everybody wants to feel special. Everybody wants to feel unique. But now let's dial back and go back to my, you know, researchers who went to study this ancestral population who are living without light. And the question is very simple. Are there also night owls and early birds among these population? The answer is no. So that means the genetic contribution, or how our genes are designed to make us late night owl or early bird, it's still there. There are undeniably, there are some people who really cannot stay awake after, say, 8 PM if the sunset is happening at 6, for example. And there are clearly some people who cannot go to bed. They don't feel sleepy even up to 1 or 2 AM. So those people exist, but they're not as frequently found as we often think. They are 1 in few hundreds or sometimes 1 in few thousand. So now, the question is, well, why we always self-describe some of us, particularly night owls. Many people say that they're night owls. They just function much better in the evening and they're more creative, they feel more energetic in the second half of the day, etc. We don't have a clear objective way to measure that. What we have seen, this is where anecdotal and personal experience also comes in. I was like, I used to go to bed at 3 o'clock in the morning. I used to work in the lab and I feel really energetic. I would come back around 1 or 2 and then still relax a little bit or catch up on some, like, email or phone calls. And then, and then I realized that, well, I was having 5 or 6 Diet Coke throughout the day. Oh my goodness. And we know that the caffeine— means I knew that caffeine affects a lot. So then when I took care of my caffeine and light exposure, uh, when I do even these days for 1 month, I said, okay, so I'll, I'll not go on caffeine. I'm completely out of caffeine. I feel like I haven't slept for a month or two. The first 2 or 3 days, of course, you have to be hydrated enough to avoid the caffeine withdrawal headache. And when I do that, there is no way I can stay awake beyond 10 o'clock at night. I become that one of those ancestral person who used to go to sleep after the fire died at 10 o'clock. And in my own family. I've seen my mom always complain that she could not sleep beyond before 11. Means I would— she lives in India, so I would call sometimes and I'm like, oh, I am wide awake. And then now she is visiting me for 3 to 4 months, and then I realized that she has an afternoon tea around 4 or 5 PM. And then I said, no, you can have only tea up to 12 noon. Of course, the past 1 or 2 days, she's like complaining, hey, my son is depriving me of the simple joy of life, and how can you do that? I raised you. I said, no, let's try this or not, experiment. It went on like 3, 4 weeks. Of course, she didn't tell me anything, but the other day I was listening to her, and then she was giving advice to her sister back in India that Hey, you know, you should stop drinking tea after 12. I did this and I have no problem going to bed around 10 o'clock. So this is some example that I— now, if you think about it, now all the listeners who are thinking that they are diehard night owls, pay a few attention. One is, when is your last sip of coffee, tea? And, you know, Diet Coke, anything that has caffeine. The problem is in these days there are many drinks, many food where we don't recognize that there is caffeine or there is, for example, dark chocolate also has elements that can keep you awake. There are also some personal food interactions. Like, for example, I'm extremely sensitive to hot chocolate. Means if I have hot chocolate, even 4 or 5 sips in the evening, for some reason I cannot sleep.

But is it the sugar, the sugar in it?

Or no, it's not the sugar. It's not the sugar. So, I mean, sometimes I, you know, I have friends who bring this German hot chocolate that has no sugar and it's very good to drink. But then I know that I have to drink that in the morning. So there are some food interactions that also affect our sleep. And then the third, another one is light. We don't pay attention to light. A lot of people are exposed to light in the evening. And then the last part is sleep. So for example, those who are night owls, they're already into a spiral because they go to sleep very late. And for many of them, the day still starts at 8 or 9 in the morning because they have a day job. So they're sleep deprived. For the first half of the day, they're struggling, they're drinking coffee to keep them awake. And then towards late afternoon when their sleep pressure is reduced, then they feel that they're more energetic. It's not because their circadian clock is like that, because of their sleep deprivation. So if you're really fighting off to stay awake in the first half of the day because— and you're trying a lot of coffee and other stuff, it's likely that you're not sleeping enough and that's putting you in a spiral. And then in the evening, you're feeling more energetic. And so that goes on. So that's why I always say that before you blame your genes, you pay attention. It's almost like, you know, if somebody is overweight, we are not going to tell, well, your genes are like that. The first thing we say is, why don't you pay attention to what you eat, how much you eat? And then, so same thing here, just pay attention to your light and caffeine intake and how it's done.

So night owls listening, if you want to do a test like Dr. Panda's mother quit the caffeine. So no caffeine after 12:00. I used to say 2:00.

2:00.

Yeah, 2:00 still works. Okay. And then watching the light from sunset. Right. So the question is always for some people, like, what time? Now, obviously, in northern regions in summer months, it can be light until 11:00 at night. So it's creating a darker environment to allow for the melatonin production and the wind down to get towards towards bed as well. But I'd love to hear back if anyone's a night owl and they try this experiment, how it goes. We can add to the list of examples together with your mother.

Yeah. I mean, there are so much about light-dark cycle that we don't pay too much attention. Another very powerful example, which is not— which doesn't apply to most of us, but some very extremely vulnerable individual is Neonatal ICUs, those babies who are born before their full term, we know that they are kept in special ICU, intensive care unit-like setups, neonatal ICU, where they have been— they are hooked up to many tubes, many sensors, in an incubator normally, right? In the incubator. And because they cannot control their own body temperature, and those neonatal ICUs are always lighter. So they're continuously lighter. And we know that their circadian rhythm may not be as apparent as adults because just like every other baby, they're sleeping, waking up a little bit, sleeping and waking up. But they do have a strong circadian internal clock. And that clock is still sensitive to light even though the eyelid is closed. Just imagine, even if your eyelid is closed, if there is sunlight coming through your room, you will sense it. So similarly, these babies can also sense it. So here is a very simple experiment done in Mexico City where this researcher wanted to know what happens if we simulate some bright light and dim light, not even dark. And in this experiment where there are nearly 60 premature babies randomized to 2 different groups, one group standard of care, continuous lighting, the other group got around 250-300 lux, which is a normal hospital room during daytime. And then from 7:00 PM to 7:00 AM, they gently covered only half of that incubator kind of setting so that at the eye level of this baby, there was only 20-25 lux of light, very dim light. Surprisingly, these premature babies were exposed to light-dark simulation They were released from hospital on an average 13 days earlier. Wow. Than females who were on constant light. There's not even a single drug in this entire world that can have this much impact. The reason why they were released 13 days early is because their growth accelerated. They said they met all the milestone growth And they— the doctors felt they are now okay. They can control their body temperature. They can be just like normal babies. And this is so powerful. There is not even a single drug anywhere in the world that's in clinical trial or anywhere that will actually accelerate the growth of premature babies this much. So that's the power of light and darkness.

That's really incredible. Is this now standard practice? And I hope you're going to say yes in all—

not in the US, but in Mexico City, yes.

You need to share this information, please. You know, you can just imagine for the parents how distressing it is as well. So to get a baby, a newborn baby home quicker than that with 13 days, that's incredible. Wow.

So this is very important because, yeah, because in the US right now, on an average, 1 in 10 live births is actually premature baby. 1 in 10. So in the US, 3.8 million babies are born. So that means 380,000 babies are born premature. Here. And I guess, I don't know about the UK and EU, it may be very similar, 1 in 10 to 1 in 12, something in that ball. So that means almost every listener might know someone who might have had a premature baby.

Feel free to share with people listening, with doctors in the hospitals, and have them listen to this as well. What, what a game changer. And it's not medication. And that's what I love about your work, is that it's not a prescription of have to take 100 supplements and you have to do this. These are all free things that are naturally available, and it's actually going back to the way the body was developed for hundreds of thousands of years. So it's really beautiful. I have one question with the detoxification at night. Is there certain standard cycles that happen? So I think with melatonin production, there's certain waves, right, when it happens as well. And detoxification, detoxification. So is there a chance if someone goes to bed too late that they miss one of the detoxification cycles? Can you talk a bit about that?

Yeah, so this is a really groundbreaking discovery that happened in the last 10 years. The scientist Michael Nedergaard, who made this discovery that in nighttime when we sleep, there's this thing called glymphatic system, just like lymphatic system in the periphery So this glymphatic system in the brain actually takes out the garbage. And as you can imagine, this is a very difficult experiment to do because people have to come to the clinic, they have to sleep, they have to be connected with different tubes so that it's not only— you're not actually sampling blood because blood sampling is relatively easy because people can sleep, you can still put a line and draw some blood. But it's even more complicated than spinal taps. Like, for example, almost every woman who has had an epidural, they know how that is done. So it's similar, slightly more complicated, actually.

So you're supposed to stay asleep, right?

I mean, while you are asleep, that's why.

Without medication. Without medication, right?

Without medication. So that's why it's so difficult to know whether there are certain stages of sleep where this thing happens. The bottom line is it is a very slow process and it happens throughout our sleep. So it doesn't matter. Just sleep as much, like at least 6.5 to 7.5 hours. And This has a huge implication and this has become the biggest discovery in sleep field in the last 20 years, I would say. And we're still trying to figure out how this is triggered, whether there are other hormones, other processes that are involved in this. But you brought up another important point, that is there are many hormones that also go up during sleep, and one of them is growth hormone. And you might think that, okay, so adults, we are not growing, why do we care about growth hormone? Actually, we are kind of growing because your body composition, like for example, all the cells I have today, they'll not be with me 10 days down the road. Particularly my gut lining will be completely new, just like the snake with a completely new skin. Each of us is putting a new gut lining in every 10 to 15 days. So that means we are shedding all the old cells and putting new cells. The same thing happens to our skin, to our cornea, the lining of our eye. Almost every cell that is exposed to outside or exposed to our food and other things inside, they are damaged and recycled. And the growth hormone plays a very important part in that rejuvenation state. And that happens only when we— and that there is a spike in growth hormone, it just spikes, big spike in the first couple of hours after we go to sleep. So then the point is, well, if you go to— if you delay your sleep time, Then what happens? Suppose I go to bed every day at 10:00, my circadian clock knows, so around 10:30 or 11:00 it cranks up growth hormone for the next couple of hours and then it goes down. What happens if I go to bed at 1:00 one day? So two things happen. One is the circadian clock will try to kick in, there'll be tiny blip in growth hormone maybe when I'm supposed to sleep around 10:30 PM. And then after I go to bed again, there'll be another spike. So that's kind of a sleep-driven small spike, but that will not be as big as my first spike. So the bottom line is, yes, you will get some growth hormone if you delay your sleep, but it is not as good as if you stick to the right schedule every single day. So that's why one point about timing and duration of sleep is maintain relatively similar going-to-bed time. So if you're going to bed at 10:00, yes, go to bed plus or minus 30 minutes or so, and you'll get all the benefits.

So it's literally the same time and 30 minutes plus or minus, and getting up at the same time, would you say?

Yeah, getting up around the same time will also help because if you're getting up without an alarm clock, that means you're cicadian clock is actually waking you up. So growth hormone, the rule of thumb is after we go to bed in the first 2 hours it peaks. Melatonin, on the other hand, begins to rise 2 to 3 hours before we go to bed. So it begins slow ramp up and then it reaches its peak maybe 4 to 5 hours before we wake up. So literally in the middle of our sleep, it reaches its peak and then it slowly goes down. I'll go to— we'll talk about melatonin when we talk about food.

And now a quick word from our sponsors. Thank you so much for your support as it helps keep our content free for everyone. This episode is brought to you by ProLon. If you want the health benefits of fasting, such as healthy aging, weight loss, energy, and mental clarity while still being able to eat, ProLon's fasting-mimicking nutrition products are for you. ProLon is the first and only clinically tested, doctor-recommended fasting nutrition program based on over 20 years of research and developed by the longevity Levity Institute at the University of Southern California in collaboration with 17 other prestigious universities. I'm a fan of the ProLon 5-Day Fasting Nutrition Program. It's primarily plant-based, non-GMO food, is shown to rejuvenate your body's cells the same way fasting would, and if done 3 times per year, can reverse your biological age by 2.5 years. Check out ProLon's 5-Day Fasting Nutrition Program and subscribe to do the program every 4 months for the best results. By going to prolonlife.com. That's P-R-O-L-O-N-L-I-F-E dot com. And for you, dear audience, get 20% off with code Claudia20 at checkout today. And now back to the show. And I know from speaking with some male friends that say that, you know, they're waking up at sort of that between 2 and 4 AM and they're like completely awake. What's happening there?

Yeah, so there are two things that may be happening. One is the sleep is not deep enough. Okay. And second is maybe they're going to bed too early, which is not happening.

Which most likely is not the case.

Okay. Which is not likely the case. So what happens is we know that we go through this REM and non-REM sleep cycle. And then in REM sleep, this is where the rapid eye movement, our eyes are moving, and this This is maybe we're dreaming. And many of us can relate that when we usually wake up from a dream. So that means our REM sleep, this is when our sleep is very shallow and we are more likely to wake up. And those of us who complain that we cannot, we wake up around 3 or 4, usually happens around 3 or 4. It's not within the first 3 or 4 hours of going to bed, it's after 4 hours of going to bed, because by that time our sleep is getting shallower, shallower, and then something internal or something external can trigger us to wake up. And so it relates to something that we call arousal threshold. What is our threshold that some disturbance will wake us up? So now when you think about arousal threshold, the only thing that we think of is, okay, so there is some noise from outside that will wake us. Oh, but actually there are many things inside our body that will also break this arousal threshold and we can wake up. Best example is, for example, people who have to go to use the bathroom. The pressure in their bladder or their colon is telling them, hey, wake up. Now you go to use the bathroom. Same thing if the bed is warm enough, then you'll wake up. You'll feel like, okay, so the bed is too warm. So what happens? We still don't understand why our arousal threshold goes down as we age. For example, a mom and the baby may be sleeping in the same bed. Mom might put the hand on the baby. The baby doesn't care. And the baby kicks the mom and mom wakes up. So that's the best example of arousal threshold is pretty high for the baby. So she or he doesn't wake up, whereas the mom wakes up with a gentle couple of kicks. And then now the grandma will wake up even if the baby just turns on the other side of the bed because our arousal threshold goes down with age. So now, how do we manage that? So what we have seen with food timing, people who avoid food for 3 to 4 hours before going to bed, so there is no food, there is no calorie Maybe only water, sparkling water, simple water. You can sell them on water. We haven't done the experiment, but the bottom line is if there is no calorie, then somehow that helps to increase the arousal threshold, what we think might be happening, or reduce the internal problem that happens in our body. So for example, you may not, um, your body may not wake you up because maybe your bowel movement or your bladder pressure will not build up. So we haven't done why exactly this happens, but what we have seen in many people, not all, avoiding food for 3 to 4 hours before going to bed actually helps them to go through the entire night or get 6 to 7 hours of sleep without waking up after 4 hours and Interesting.

Is there any correlation with insulin levels in the blood?

We haven't done any of that. It will be interesting because I know that there are a lot of people who are not type 2 diabetic or pre-diabetic, they're completely healthy, but they still wake up. For me, what I have seen is when I'm in new hotel room with a new bed, sometimes certain hotel brands, their beds actually warm up. So I wake up around 4 o'clock on a warm bed. My rule of thumb is when I'm booking a hotel room, I always ask for two queen beds so that I can just go to sleep.

That's a good hack for people who travel a lot. That's a great tip. Thank you for that one as well. There's obviously mattress cooling devices.

Yeah, but you know, you cannot carry all these devices. So the best is to roll over. All go to the other bed.

Exactly. Okay, wonderful. Thank you for clarifying that. Let's look at nutrition and time-restricted eating, a.k.a. intermittent fasting. This has gotten a lot of publicity. A lot of, a lot of people have tried different versions of it. But before we sort of dig in, can you explain sort of generally what the concept is around time-restricted eating and why it's so important?

Yeah, so far, as I mentioned, we believe for a very long time, we still believe that the light is the biggest time giver, entraining stimulus that entrains or synchronizes our internal clock with the outside world. And light goes only through the eyes, so that's why light is so important. But over the last 23 years, starting from 2000, people did some simple experiment saying, well, if light is important, and what is about food? The reason is, in our liver, gut, and all these digestive and other metabolic tissues, there are many genes, many enzymes that are involved in digesting food, absorbing nutrition, converting that nutrition to energy, or converting that nutrition to various chemicals that are essential for our body, all of these things actually turn on and off at different times. So that means there is a circadian rhythm to that. So that means in the morning when you wake up, the clock in our pancreas is cranked up so that for the first half of the day we can actually eat carbohydrates without too much spiking of glucose, or the blood glucose will come down. So all these things happen. So then the curiosity was, well, are these all driven by the brain clock that's tied to the light, or there is some connection with the food? And many labs, including my lab, we figured out that no, actually food, when animals eat, because all these experiments have to be done first in animals, lab rats and lab mice, When mice eat, particularly after several hours of fasting, it's a very powerful timing cue to tell all these peripheral— we call it peripheral organ because they're outside the brain, gut, liver, etc., heart. They actually track when these mice ate. And the clock, the timing, the counting of time, you can say, kind of starts from there. So that means Suppose, say, we feed mice every day at 6:00 PM because mice are nocturnal, they're night active, they prefer to eat at night. So every day, if we feed mice at 6:00 PM, then their body's metabolism, circadian clock, everything is tuned so that starting from, say, 4:00 PM onwards, their digestive juice and everything will accumulate, and then the body is primed to digest that food. So 6 o'clock, 6:00 6 PM, we give food, bam, there everything is ready so they can process that food pretty well. And if we give that food, for example, one day instead of giving at 6 PM, if we go to say 10 PM at night, then all these preparations have happened, but then the food didn't show up. And it's almost like inviting somebody for dinner, you have prepared everything, and then no show. The guest is 2 hours late. What happens if food is still and cold and you're not that excited? You still entertain your guests, but it's not as good as you expected. The same thing happens when you miss time. You have been so habituated, your clock is so habituated to digesting, assimilating food so well. And when the food doesn't appear on time, is delayed, then the digestion, all these processes happen, but not as efficiently as it would have been. The same thing might happen if the food shows up earlier, it may not get digested, it will just sit there for a few hours before it's well digested. So that's what we found, that when food appears, and if the food appears at the same time every single day or most of the days, then that triggers all the circadian rhythms so that the body is prepared to digest that food. So now, So this is one concept. The second concept is, okay, so the food has to be eaten after breaking a fast. How long that fast should be, right? So this is where all the argument comes. Good question. Like, yeah, what is fasting? How long is the fast? So now we gotta go back and think of not in mice because mice digest food much faster than we do, but in humans, for example. So if I finish my dinner, say at 6 PM, I have a good healthy dinner or whatever I ate at 6 PM, my mouth stopped eating. So from my mouth, the fasting might have started, but then the food actually went to my stomach.

True.

Yeah. And then it will stay in my stomach being digested for the next 5 hours. And so for the next 5 hours, my stomach is not getting rest. It's actually not fasting, it's digesting food. And then after 5 hours, it will leave stomach and it'll go to the intestine where the nutrition absorption will happen. So that means from 6:00 PM till 11:00 PM, although I'm not eating, my stomach still has food. And is still absorbing food, it's not fasting. And then if we think about our gut lining and the stomach lining has to be repaired. So suppose I went to bed at 10 o'clock or 11 o'clock, my growth hormone will spike around midnight, and that's when it'll tell the repair crew to come and relay or repair the gut lining. So that's when all the repair is happening. And that process is not just instantaneous. Those of you who have seen how the highways are repaired, it takes time. So you can imagine that that's another 6 to 7 hours when this repair happens. So now you can imagine that, okay, so 5 hours, although my mouth started fasting, my gut is not fasting. So there's still 5 hours of digestion. And then you add 6 to 7 hours, at least 7 7 hours when the repair has to happen. But I'm saying that the stomach stopped its role, but the small intestine and large intestine, they still continue absorbing. So there is still work going on. So that's why the actual fasting, being withdrawn from actively eating food when it is at least 12 hours, then we know that, okay, so the body actually went through the daily cycle of absorbing nutrition repairing the gastrointestinal tract. And then for the preparation for the next round of food, as I said, again, all the digestive juice have to be prepared and kept ready. So that's another few hours. So similar. So if you add this up for humans, at least 13 to 14 hours of overnight fast is what is needed for this cycle to repeat again in a healthy way because you can eat. Nobody's stopping you from eating. But then two things is happening. Yeah, you cannot digest and also you cannot repair. So, so this is how the concept of time-restricted eating came because we thought it's when it comes to nutrition, people always thought with very strong foundation of scientific foundation that the number of calories we eat is important. Of course, that is important because I just can't go and eat 4,000 kcal and then say why I'm getting fat. I know. That's fair. Second, number of calories do matter. And second is the quality of nutrition also matters. I can't just go and eat ice cream only and then say, complain why my blood sugar is going up. So those two things matter. But the third thing that we found is timing is very important because particularly how long we fast. And when we started this concept, because it started in my lab 12 years ago in 2012, and I remember struggling with the title of the manuscript because this experiment was done in mice and the experiment was very simple. We took two groups of mice, identical mice, same age, same gender, same— born to the same similar parents in the same room, had the same gut microbiome, ate the same food and the same number of calories every day. The only difference was the first group ate whenever they wanted. There was no barrier. And the second group, they were allowed to eat only for 8 hours in the first experiment. And within 8 hours, they ate the same number of calories as the first group. So there was no difference in number of calories, no difference in quality of food. Both groups got actually high-fat, high-sucrose, really unhealthy food. And to our surprise, the second group, which time-restricted, um, because they were eating only for 8 hours, the consistent 8 hours, we didn't move that 8 hours, they were completely prevented from obesity, diabetes, liver disease, um, heart disease. And they had way much more endurance. There was a surprising fact that it's not that they're fasting and they're feeling really crappy about life. They were actually more active, they're full of energy. They could stay on the treadmill twice longer than the mice that ate ad libitum. So then we thought, okay, so what should we— what should the title of the manuscript should be? And then we said time-restricted eating, because we are not changing quality of calories, not changing the quantity of calories, we are just changing the time. We're restricting the time, no calorie restriction. And we did not use the word fast because there are a lot of people who actually need to fast, but then they don't want to fast because they hear starvation when they hear fast. Yeah, fast is a very bad four-letter F word for them. So they really don't. So that's one aspect. And then the other aspect is, well, we— fasting is very ill-defined because For example, sometimes people ask me, "Hey, do you fast?" I say, "Yes, I fast between meals." Which is true.

Whenever I'm not eating, I'm fasting.

Yeah, exactly. Yeah. So, it's very difficult to define that fast. So, that's why we said, "Okay, so we'll just do this time-restricted eating." And as you said, this became— this fell under the umbrella term, which is intermittent fasting, because before this experiment, intermittent fasting essentially meant few things. One, you can fast every other day, which is called every other day feeding. And scientific literature, it can— it could also mean fasting for 2 days in a week or 1 day in a week. It also meant reducing calories only for 5 or 6 days in a month or 2 months. And when this time-restricted eating came, it was kind of mouthful. So then people said this So these days when you say intermittent fasting, most people will think, yes, you are doing 8 hours of eating, 14 hours of— 16 hours of fast. Yeah. So we have done this experiment in many different ways. Coming back to your other question, related question, different forms of intermittent fasting. In mice, we cannot go below 8 hours because when you go below 8 hours, then mice eat less.. And we know that reducing calories or calorie restriction has many benefits. So we cannot figure out whether it's the benefits are due to reducing calories or eating within a short window. So these experiments are not doable in mice. In humans, people have done these experiments. They ask people to eat within 4 hours or 6 hours. And as expected, they also reduce their total caloric intake. They eat less. And of course, there is also benefit, but we cannot clearly say whether the benefit is from reducing calorie or eating within a very short period, 4 hours or 6 hours. There's some studies where it's very well controlled, healthy human volunteers are either asked to eat everything within 12 hours, that's the control, or 6 hours. It's very short window, but I know this is experiment. We are not asking people to do this every single day. And in those experiments which came out of Courtney Peterson's group at University of— who is at University of Alabama, Birmingham now— they found that even though the second group that ate within 6 hours at the same number of calories, they still benefited in many different ways, including improvement in blood sugar control, blood pressure control, And although these people are not too sick to begin with, so they were a little overweight, but not incremental benefits. Yeah. So the benefits are there. So that's why we said the time-restricted eating is still a valid approach to do a nutrition. One can combine it with counting calories and paying attention to quality of nutrition.

Quality. Yeah. Eating whole foods. And I'm not a big calorie-counting fan, but I think it's quality of like whole foods and sort of the peripheral of the supermarket is generally a good rule of thumb. Avoid those aisles, right?

I mean, I guess the biggest challenge in nutrition, there are two big challenges. One is a control for time. Like, we almost think that our, our body, our human body is like a machine or a car. People always give that similarity. And, you know, machines and cars, they will run whatever time it is. And you can fill up your gas tank in a car any time of the day. It doesn't matter. But we are not like that. The difference is you can drive your car whatever time you want or whatever you do to it, but you have to take the car to the repair shop, to the machine shop, or to the— for its regular maintenance. Somebody else has to service your car, whereas our human body is designed that if the body can service itself, because that's what happens with circadian rhythm, that period of fasting, that period of sleeping and aligning fasting with sleeping, that's the best repair mechanism and nothing can— there is no repair stuff, no, literally no, there is no drug, there is no procedure in hospital that can actually substitute for that repair process. That's so valuable. So that's one aspect is we are not paying attention to timing of nutrition. We feel like we can eat any time. And then the second thing is beyond circadian, the problem is we don't know how to prepare a meal. We don't know how to cook. So then when we don't know how to cook, then the quality of nutrition, we just depend on what is written on the food label. And Everything goes south. So with time-restricted eating, what we're finding is very interesting. In many studies, what people are finding, if they're only told to eat within, say, 8 hours or 10 hours— most of our studies, we involve 10 hours because what we found is for average people, 10 hours is a good target. Of course, there are some who really want to optimize, they're into biohacking and other stuff, they can do 6 hours, they can do 8 hours. 8 hours. But for most people, it's 10 hours. What we find is when people go through 14 to 16 hours of fasting overnight, next day when they're eating, typically breakfast is the healthiest food or meal of the day for a lot of us if we eat breakfast at home because we have complete control over what we're eating and how much we're eating. So what we find is people eat a healthier breakfast. And since they eat a bigger breakfast, and breakfast doesn't mean morning meal, it's after the 14 hours of fast or something. Yeah. Then they don't snack until lunch. So the number of snacking also reduces. And most of our snacks in modern days is really high sugary treats. So that reduces. So it improves food quality. And since the kitchen closes, they stop eating at 6, 7, or 8 o'clock. If you think about it, almost all of our addiction, whether it's alcohol or whether any sweet treat, whatever bad food we are addicted to, that happens typically late at night. So people reduce their alcohol intake. And this is, we're finding in many different studies. And they also reduce their late-night ice cream intake. And in fact, in my house, we have seen this since I used to be— the number of beer bottles or the wine bottles we used to go through before and after has dramatically changed. Now you know. Amazing. So in a way, time-restricted eating or intermittent fasting, although people pay attention to timing, it indirectly improves their nutrition quality and also reduces some calorie content.

And I'm curious, a few different points I want to touch on. What is the minimum time you would recommend? So is it that 14 hours that you were saying in order to have that cycle, those 13, 14 hours overnight? And then differences between men and women, particularly around hormones for, for women?

Yeah, so this is a tricky question because what I believe is anyone from 10-year-old to 100-year-old can at least fast for 12 hours, okay? Yeah. Whether healthy, unhealthy. And most listeners will think that, huh, I'm already doing that. But actually, that's not true because when we objectively measure when people are eating, where people have to log every single thing that they are putting in their mouth or Everything from water to all calorie-dense diet. And of course, we figured out which— we discounted water and some black coffee and other stuff. What we found is when we go from consistency, like within 10 days, are you really sticking to that 12 hours or not? We found less than 10% of people consistently eat all their calories within that 12-hour window. Less than 10%. We were surprised. And these are not shift workers. These are just regular people, all staying home, retired, etc. So that means at least once or twice a week, we are eating either very late at night or we are waking up very early to go somewhere. For example, when I travel, I get up early, although I'm not eating. When I go to the airport, I see 5:30 or 6 o'clock in the morning, there's a long line in front of all these food places. So this is another example you are working on. So the point is, are you consistent within that? And that's why I believe anyone from 10-year-old to 100-year-old can and should eat within 12 hours if they're healthy. It's almost like brushing your teeth every day, right? And then the question is, if you want to improve your health, Then the question is how far away you are from optimal health. So for example, if all your blood pressure, blood sugar, blood cholesterol are perfectly normal, you don't have any autoimmune disease, you don't have any joint problem, nothing, you're mentally functional, you're sleeping 6-7 hours. Yeah. And you're eating all healthy food. You have no problem, nothing whatsoever. Then Yeah, you can eat within, say, 10 hours, or occasionally you can go to 12 hours. It's not a big deal. And you might see— then the question is, what improvement I will see? And this is where, personally, for example, my target was to hit the age of 50 without being on any medication for cholesterol, sugar, and blood pressure. And I achieved that. But then, you know, once in a while, I would get acid reflux. Heartburn. And when I eat within 10 hours or 12 hours within that window, I don't have any heartburn. I said reflux. So that means I'm fully productive. I'm not worrying about my, my gut health. And when I eat within this 8 to 10 hours, then obviously I'm also finishing my meal 3 to 4 hours before going to bed. So that means I used to wake up at 4 o'clock, just like you mentioned. And when I stop eating 3 to 4 hours before going to bed, I sleep continuously for 6 to 7 hours at least. And so this is another example where if you're healthy, you can still do it because it's good for your sleep. And then next day you're feeling more energetic and your executive function for the first half of the day goes up. Now, coming to people who have blood pressure, blood sugar, or blood cholesterol, Whether or not they are on medication or not, this is where it becomes a little tricky because you don't want to fast too much. So, for example, 8 hours of eating, 16 hours of fast, depending on your blood sugar, how it fluctuates, we cannot say. So this is where you have to consult with your doctor. But if it is blood pressure or blood cholesterol, maybe 8 to 10 hours of eating and the rest fasting. Might help you. In fact, almost all time-restricted eating studies have shown improvement in blood pressure, whether the person was taking any blood pressure medication or not. And for cholesterol, it takes a little bit longer. And also diet quality has a huge impact on blood cholesterol. So this is where people have to control. Now, when it comes to weight loss, because everybody wants to lose a little bit weight, which is understandable because 70-plus percent of people in the Western world, and now even in many other countries, that percentage is increasing, have some extra weight. And this is where it becomes a little tricky because do you want to do 6-hour eating or 8-hour eating? And then if you— once you lose the weight that you want, then should you stick to it? And then how much weight you lose. So when I, for example, a couple of weeks ago I was in Chicago and I completely non-work-related convention, nothing. I was not expecting anybody to come up and even recognize me. And then somebody came up to me and recognized me and said, oh, I should thank you because I lost 55 pounds and all that stuff, like 20+ kilos. And then there was another guy, he came and said, oh, I also lost 14 pounds. And then the first guy was telling the last guy, "Look, I lost 55 and yours is nothing." He said, "Well, it depends on where you started." Yeah, it's all relative. Exactly. It's all relative. And then there was another third person who came and said, "You know, I was doing everything, I'm already healthy, but I tried what you said before on one of your podcasts and now I'm sleeping better. And that gives me a lot of energy in the first half." He's retired. He said, "Now I'm involved in many non-government organizations, volunteers." So all these, I just bring the joy of life because I'm more energetic. So here is an example of 3 different people with completely 3 different kind of outcomes. Yeah. One who says he lost a lot of weight, but he did not have any other problem. Although he was obese, he actually had, surprisingly, he had completely normal cholesterol and everything. The second one who lost 14 pounds was on blood sugar medication, blood pressure medication, and also on statin. And now he's completely off of all 3. And of course, he said that, well, it helped me also pay attention to my nutrition because he's now eating better nutrition. And then the third one who is completely healthy is talking about his health. So this is all males. So now coming back to women, what I have seen, there are many women that benefit. We have an open app called My Circadian Clock, and we also have another commercial app now, On Time Health. People can go to Get On Time Health or My Circadian Clock. On My Circadian Clock, I get emails once in a while, and a common theme that has emerged is many young women, premenopausal women, they would try everything. They try to eat within 8 hours, they want to overdo it, so they say, okay, I'll try 6 hours. And then they are eating very healthy food, a lot of leafy greens, salad, and a little bit of grains. They're also running 5 miles a day. So guess what? They become amenorrhoeic because they are in a negative energy balance. They're eating less than what their body actually needs. So they lose their hormone cycle and they become more cranky and they complain that this is not working for me. So this is where paying attention to your nutrition intake when you're doing Timeless Eating, and also whether you're exercising or not, becomes simple. The second thing that I have seen, the other better side of the story I have seen, is from a high school teacher. She was also premenopausal, but what she found, she, when she did it, she found that it made her cycle more regular.. And she was exactly on 48 days. And then she said, oh, this is really interesting. And being a science teacher in a high school, and she was also kind of a counselor, um, unofficial counselor to many, uh, girls in the high school. She knew that many girls, they would miss a period or they're late and they would become very anxious. And then she said, okay, so why don't you try this? Let's try, all of us try like a 10 hours or 12 hours time-restricted eating challenge and then see what happens. And surprisingly, she found that all of these girls became completely regular. They got their period in 28 plus or minus 1 or 2 days. And that's when she contacted me. And actually, I was invited to a nice dinner at her home. And she said, look, this is what I found. Do you want to do a clinical, like a human study? I said, well, it'll be really difficult because First thing is these are minors and I have to get parental assent and then parents. So, so this is some anecdote. Yeah. But I have also seen from other people who were trying to have children and they had some trouble, they tried it with optimum nutrition, of course, and they could conceive. So then they would come send me email or sometimes even invited me and then I This is why you're flying around the world. So for women, it's a little bit tricky. For now, postmenopausal women, we do see that it does reduce the risk for cancer. And also many postmenopausal women who already have breast cancer, the chance of relapse reduces. And this is another experiment done, another study done in neighboring institute, University of California, San Diego, where they retrospectively looked at women who had breast cancer and were reporting, self-reporting 13 hours of overnight fast or not. They found that those who are fasting at least for 13 hours or more, they had reduced chance of breast cancer relapse. Wow. And That was significant. And now researchers have gone back and redone that experiment in laboratory animals where they wanted to see, okay, so now, because, you know, in all human epidemiological studies, there are many variables we don't know. This is a smoking gun, but we don't know whether we can connect it. So that's why, again, independent researchers, not in my lab, they have gone back and tested and they find the same thing. That those who fast in animal studies, if they fast over— sorry, consistently for 14 hours to 16 hours, then two things happen. They are less prone to getting the cancer itself, even though they were transplanted, even though tumors are placed inside the mammary fat pad. And second, if the tumor is placed and the tumor doesn't grow as aggressively as in the animals that are fed randomly, that eat at any time. So at least for postmenopausal women or premenopausal, or breast at high risk for breast cancer risk, this is important that it reduces the risk for cancer. And we do see, you know, cancer survivorship is a very big thing because in the U.S. alone there are 15 million people who have survived cancer. And those who survive cancer, because of the chemo and other treatment, there is a lot of stress on their system. Many of them, they struggle with their heart issues, some of them struggle with their glucose control and mood issue. And this is one thing that we would like to do because we want to see whether cancer survivors can stick to time-restricted eating, and can they reduce the risk for heart disease and other diseases? Um, the epidemiological studies show that yes, there are benefits, but there has to be intervention studies to put it to practice.

This is really, really powerful. And I just want to summarize for women, because I had been looking at this and I had tried, um, I was like those teenagers or young women you were mentioning, like I've tried a whole skew of different things as well. And depending on which phase of the month it was, I found that it was either energizing me or not, but I was literally reducing it down to sort of eating windows of 6 hours a day or sometimes even less at times, but sustaining that. But I think one major point you made is to look at two things. One is exercise. So I like to be active. I do a lot of exercise and movement during the day. So just to— if there's more exercise, to make sure that the the healthy calories being consumed match that. So is that, is that the point? So would you not see any risk in women doing, you know, 6-hour eating windows, but just ensuring that the caloric load, basically, of healthy calories consumed is enough to match what is needed for the body to function on a daily basis?

It's really hard to make that call because And being an experimenter, we really don't know what will happen because there is— what's the window? Yeah. No, we always think about the immediate impact. We don't think about the long-term impact because particularly this is, this is a problem that's very close to my heart because we are doing now studies on what is called relative energy deficit in sports because nearly 42% of athletes, both male and female, They are in an energy deficit. That means they're eating less than how much their body is spending. And in these cases, we, um, this is so widespread, but still there is no animal model because you cannot sample their blood, their organs, et cetera. So what we are doing that, and we are finding that there is so much impact of this There's so much adverse impact of relative energy deficit because it compromises your bone health. And you may not see how it is compromised right now because you may be very strong, you may not be hitting a wall or falling, but 5 years or 10 years down the road, if you have really low bone mineral density, that can hit you there. Or if you have microfractures. So that's one thing. And another thing we are also finding in animal models, these SREDs affect different organs. In females, it affects the uterus, in males, it affects a lot the kidney. And the impact is all over the place. Like in the brain, it affects the depression and anxiety center of the brain. So that's why I'm really hesitant to say whether somebody should go eat within 6 hours. The problem is if you're eating within 6 hours, there's a good chance that 1 or 2 days in a week you may not have the time or you may not have access to good nutrition to eat enough. And that's when you might lose your performance 1 or 2 days, then you'll blame. And I know you're on the knife's edge at that point. Okay, so make a little bit of mistake. So that's why I'm very hesitant to say one should do 6 hours. Yeah, that's why 8 to 10 hours is a good rule of thumb.

Yeah. Okay. No, but I think that's good because I'd love to ask you, like, before we finish up, for optimizing longevity and from the research you've done and what you've seen as well, what would be— and I know people are different, etc., but sort of for a general healthy person not taking medication or either or— what would be your protocol that you would say?

From eating and sleep. Yeah, I would say there are 6 points we have to keep in mind. Number 1, try to maintain a regular time to go to bed and be in bed for 8 hours so that you can get 6 to 7 or 7.5 hours of sleep. Because when we sleep well, then brain and body actually repairs itself much better, get reset, rejuvenated for the next day way much better. So that's number 1. Number 2, after waking up, try to wait for at least an hour or ideally 2 hours before your first meal of the day, first calorie of the day, because that's when your sleep hormone, say melatonin, is slowly coming down and your stress hormone spikes reaches its highest level within an hour of waking up. And you don't want to eat when your stress hormones are pretty high and your sleep hormone is still mildly elevated because your body cannot process nutrition pretty well. So that's number 2. Number 3 is try to have breaking the fast or breakfast at consistent time. So it's— breakfast is not the first meal that you eat right after waking up. It's actually the meal that you are eating after at least 12 to 14 hours of fasting. So try to eat the first meal at a consistent time and then eat all of your rest of the calories within the next 8, 9, 10, maximum 12 hours, never beyond 12 hours. And then the last meal should be— so that's the number 3. So let's stop there. And then the 4th one is try to step outside during the day, ideally the first half if you can, to get at least 30 minutes of daylight or sunlight. If you cannot, it's okay. You can get any time, 30 minutes of daylight is good enough for average person. And then the fifth one will be exercise. Those, um, any exercise is better than no exercise, no doubt about that. But if you want to get the best out of your exercise and reduce the risk for injury, then afternoon exercise is much better than exercise late at night or early morning. Afternoon exercise has been shown to significantly reduce blood pressure, reduce blood sugar than the same exercise in the morning. And since the body is warmer and the joints are more flexible, there is reduced risk for injury. That's why afternoon exercise is much better.

I thought first thing in the morning is beneficial in terms of blood flow to the brain for BDNF benefits.

Well, the thing is, if you look at activity of ancestral population, their morning activity, they have a spike in afternoon activity. There's no doubt about that. But the morning activity is much higher than the average person's activity spike in modern world. So, so what I say is, in the morning, if you really want to be— if when people have plenty of time, at least go outside, go for a walk for 10 or 15 minutes, and This is very important, particularly for college students and high school students, because, you know, a lot of them, they haven't had enough sleep. So for them, really going out in the morning and getting that morning light and, you know, they're healthy, they can run, and they can do some activity, that's way much better. I'm talking about for the regular folks who are, you know, beyond 50, and then they have a little bit of time, they cannot go every day. Okay. Yeah. So then afternoon is better. Yeah. With number 6. Number 6 is your last meal should be at least 3 hours, ideally 4 hours before going to bed. And in this last 3 hours before going to bed, you should also dim down your light.

So dim light and no food. And ideally meditate or do something, read a book, right?

Yeah. Calm the nervous system. So, these are the 6 simple foundations for circadian rhythm. And I guess almost everybody will benefit one way or the other by following this.

Yeah. And for people listening, I'll put a summary together with this podcast episode of Dr. Patchin Sunda's ultimate longevity circadian rhythm optimization. And before we finish up, I'd like to ask a question.

If you could live to 150 years old with excellent health, how would you spend it? 150 years? Yeah. So the idea is very simple. In every 10 years, you have to reinvent yourself, do something new. Like Madonna. Yeah. I mean, she's actually— she's an amazing person. People love her or hate her. But that's what the sign of successful people are. Yeah. Yeah, they're very polarizing. No, that's, that's true in everybody's life. Like, we have to reinvent ourselves. We have to do something new. And when I look at my own personal professional career, the first 10 years was light. The second 10 years was time-consuming. And then now I'm really interested in this exercise and the balance between exercise and nutrition, how the optimum balance can drive a lot of performance, and then the suboptimal balance can feel good now but can have adverse effects. So similarly, every 10 years come up with a new idea. I mean, the world is so big, there are so many interests. Just live full of life.

Yeah, stay curious. I love it. Where can people learn more about what you're up to, and what would you like to share with people? Any websites, donations for your lab, social media, etc.?

Yeah, so many of my research that actually made headline, for example, the discovery of blue light sensing protein and then time-restricted eating, many of these were not funded by federal grants that typically funds research, but those are mostly funded by philanthropy foundations, etc. So that's why when individuals, whether it's small donations or big donations, doesn't matter, when they donate to my lab, they can donate by panda.soc.edu/giving. And I guess, or donate, I guess you can put it on the show notes. Then that helps us to go try risky, high-risk, high-impact kind of experiments. And so that helps. Even small donations help in the sense we have a lot of young trainees who could have gotten a much better job, you know, selling products or writing codes for big tech companies, but they decided to do science.. And these donations help them to go to conferences, meetings, present their work. And sometimes they have young children, they can find daycare for their children when they're going and doing, going to conferences. I remember there was a nice call for funding by Jonas Salk because I, you know, I work in Salk Institute, Jonas Salk, who made the polio vaccine. And she had this call. She said, well, you know, this was in the '70s, right? So things are very cheap. I said, your $1 donation will buy a lab coat for the researcher and your $1,000 donation will give the researcher all the reagents he needs for one week.

So prices have gone up a little bit since then as well.

So that's one. And then second is I am, um, I try to be active on Twitter. So my Twitter handle is Sachin Panda. And then also I try to be active on Instagram, Sachin.Panda. And so those are the two. And then we do have two different entities. One is mycircadianclock.org. That's a research app people can download and sign up and share their own have it with us. So that's completely research, so we don't sell any information. Every— all the data is anonymized. And then I also have a commercial app called Get On Time Health, and this is for people to pay a little subscription and then track how they are following their circadian rhythm. So those are some of the resources people can have access to.

Perfect. And we'll link everything in the show notes. Sachin, do you have any final ask, recommendation, or any parting thoughts or message for my audience today?

I think people always think of longevity as, as you said, living up to 150 years or something like that. But in my mind, longevity starts every single day. Every single day we should feel like we are at our peak performance. We beat our yesterday's performance, something like that. To be healthy in single— every single day is what matters. And those of you who are not thinking that why should you live up to 150 years or 100 years, or why, why should not enjoy your life now by engaging in unhealthy habit? You know, being unhealthy is very expensive. It's not easy. You might think a shortcut, but it's very expensive for you as your medical bill. It's also socially, emotionally very expensive and taxing for all the loved ones around you. Because when we fall sick, we become a burden on our loved ones. And the best thing we can give to our loved ones, whether it's our children or spouse, is to give them a worry-free day so that they are not worrying about my health, my disease, my doctor's appointment, etc. So that's the That should be the drive to live healthy.

Yeah. And arguably, if you're living healthy today, you have more energy, you feel more vibrant, and you're actually living better and having more fun too. So on that note, thank you so much. I know we've gone on for quite a while. I just saw the time. Thank you so much for your time today. It's been such a pleasure to have you on and sharing your wonderful work.

Thank you so much. Thank you. And have a perfect circadian day.