 They lose six years off their lifespan and they get exactly the same list of diseases as the people who do night shift work All right, or have sleep apnea. All right. Why is that these things are feeding into the same biological pathways? Okay, and that's where they deliver their benefits. Okay, so circadian rhythms are really crucial all of these things I Most of our lifestyle influences on health work through our circadian rhythms. All right now. Why are circadian rhythms so crucial? well Think of these Deaf dumb and blind movers trying to move a sofa. All right, they have no ears and mouth so they can't talk to each other All right, but they need to lift at the same time They need to walk in the same direction or else the sofa is going to fall down All right, so they need to coordinate their activities, but if they can't communicate, how do they do it? All right, and Our cells are in that situation. Our cells need to cooperate with all the other cells They need to achieve Biological things that they can't do alone. They need to do it with a cluster of other cells like an organ Everybody needs to be working together but they need to all do it at the same time they need to be all be running the same program and How do they achieve that? They achieve it through clocks. All right, and they all have to have their clocks synchronized if they don't have their clocks synchronized Then they won't do it. So all of our cells. They've got a biological program at this time of day I'm going to do this. All right, and if all of our cells are Have the same time Then they'll be able to interact with each other successfully and all the functions of our bodily functions will be executed well All right How do we give time to those clocks? All right, how do we get all the clocks ticking and all of them synchronized? Well, there are five main ways. All right, one of them is light exposure. One is exposure to ambient temperature One is through social interactions one through exercise one through meal timing Okay, so let me talk a little bit more about each of those How does light give us our timing well? It turns out when Light mostly blue light but also ultraviolet light and a little bit of green when it strikes our retina There are some special receptors that send signals to a part of the brain called the suprachiasmatic nucleus Which is where the so-called central clock is located. So it's a single most important clock in the body And that portion of the brain sends signals up to the rest of the body. This is what I think the time is All right, so that's a very important clock and what drives it Blue light is really crucial. All right, and everything from about here on yellow up Can affect it somewhat but basically red orange and yellow with no green is Has no effect on the central clock. All right, so what does that mean? In the nighttime you can use red orange yellow light with no problem All right, it won't have any effect on your circadian rhythms. It won't tell your brain that it's daytime Okay, but in the daytime You really need all this blue light. So whenever you're exposed to blue light. It's telling your body. It's daytime okay, so By day you need to get sunlight And when you're indoors during the day you need to expose yourself to bright full spectrum lighting All right now what kind of lighting do people actually buy if you look at these lights? You'll see they have a yellowish tinge to them. All right And that's the worst possible kind of lighting to buy. I don't buy anything It says cool white bulb. All right that that's uncool Okay, what you want is you know something with a color temperature of at least 5,500 Kelvin and And it should be it should look a little harsh. It should look very bright very blue. All right like the you know think of the halogen headlights and What should things look like at night? They should look like a campfire. All right campfire Color temperature more like 600 Kelvin. All right, and it's very red very yellow And very little blue Okay, so these yellow lights they have too much blue though disrupt your night But they don't have enough blue to untrain your day. All right, so now It turns out Since Thomas Edison invented the light bulb. All right, he's You know a great man in many ways, but he really damaged our health with that one and so we now have these light bulbs all around us at night and It turns out that having all that light at night is probably disrupting our health and So for instance light exposure at night is closely tied to obesity rates So in this study, they split light exposure up into three groups a low light group middle light third and a high light third and the darker the light, you know, basically The people with middle amounts of light exposure at night at 10% less obesity than people with highest light and people with the lowest light exposure at 20% less obesity and We know that circadian rhythm disruption causes obesity In animals, so this is very consistent With what we know. All right temperature really important We want to be exposed to warmer temperatures in the day cooler temperatures at night now in our natural environment outdoors That happens automatically. There's no place in the world. You can go where it's hotter at night than in the day Okay But now that we have artificial control of our environments, what do we do? Especially if you're in the south You put air conditioning on all day so it's cool and You go through offices the mall everything's, you know, very cold And then you get home and you want to save money on energy And so you turn the air conditioning off and now it gets warm. So you've reversed the day night cycle All right food extremely important Circadian rhythm and trainer It's very important to do intermittent fasting have an extended overnight fast You should never eat any calories at night And you should have at least a 12 hour night So once it's nighttime for you don't eat any more calories and you should actually extend the fast longer than 12 hours So I generally do about 16 And I think that's about optimal you have to be make sure all of your food comes in in the daylight All right, so what happens? These are two groups of mice in this black line The mice had their their food fed to them Equally throughout a 20 the 24 hours of the day All right, and mice when they get food they just go eat it if they're hungry And so these mice were eating all day. No circadian rhythm and treatment The other mice they got exactly the same food. All right, but it was just within a restricted window an hour window And what happens they live 50 percent longer All right, that gets back to what I said about the fasting Our bodies really need a fasting period to go cannibalize themselves and clean up all the junk And then they need a feeding period in which they reconstruct themselves And you're short circuiting that if you're always feeding yourself through 24 hours, you're never cannibalizing yourself because Disposing of this food that came in is a higher metabolic priority and it trumps that all right So if you're feeding all the time Then you're never cleaning up your body and it really shortens your lifespan all right Now also meal timing when you eat so you need to need to be on that Fasting feeding cycle, but then what's the optimal time to feed? It's between about noon and 4 p.m. All right, and but you want to get all of your food intake in the daytime Okay, and it turns out it used to be said that skipping breakfast was bad for your health It turns out that's not true Skipping breakfast is good for you Because it helps concentrate your food intake But skipping breakfast is terrible if it leads you to eat food at night. All right, so Late night eating is really bad for you And leads to obesity and other problems. All right, but if you don't eat at night skipping breakfast is just fine All right, one last thing about Uh The meal timing issue. This is another reason why diets tend to fail. All right when people are trying to lose weight They wake up in the morning. The brain is fresh. They have a lot of willpower and so they say all right I'm not going to eat. Okay, so they restrict their eating. All right, and then as the day goes on they get hungrier and hungrier and By the time it's nighttime their brain is tired. So their willpower is lower All right, and then they give it they give in and they start eating so they're eating at night And so what have they done? They totally reverse the circadian rhythm And they're feeding at night and fasting in the day and that's very disruptive to their bodies to their health And it leads to weight gain All right physical activity all right the keys In the daytime we need to get exercise or activity We need about 30 minutes of moderate intensity exercise per day Modern intensity is where you're working fairly hard, but it's comfortable and fun You know your your breath your heart rate Are just about if you if you exerted yourself a little bit harder your breath would get rapid Your you know your pulse would get too high. It would be unpleasant You'd have to be you'd feel like you were working hard go just below that point That's moderate intensity if you get 30 minutes per day Then you're getting enough to train circadian rhythms If you do it every day over time it builds up a level of fitness This is from a long-running study Started in the 1970s where they give people a treadmill test to assess their fitness They also started assessing strength later and Then they track them And see how long they live see what health problems come up And it turns out if you were in the Low level of cardiorespiratory fitness compared to the high level people in the high level fitness have 75% lower mortality over the next 10 years All right, so exercise and fitness does have a huge impact, but Just more and more fitness is is not better. All right, so what happens when we look at different levels of activity Well, it basically follows a line like that red line Then i've gone as you go up to about half an hour a day of moderately intense activity You keep improving your health, but once you reach that point Then further Exercise increases your fitness, but it doesn't increase your health it no longer reduces your risk of dying All right, why is that it's not fitness that prevents you from dying. It's circadian rhythm and training and Once you've gotten that 30 minutes of exercise you've been trained your circadian rhythms as much as you're going to all right another important conclusion When we do a circadian rhythm and training thing The effect persists for about 36 to 48 hours All right, so what does that mean if I exercise today? I get the benefits for 36 hours All right, but then the benefits the benefits have lapsed I need to exercise again in order to get the benefits All right, and it's the same with all of the other circadian rhythm and training things you need to do them every day If you miss one day Then you have to say i'm absolutely not going to miss the next day never miss two days in a row All right, then you've uh, totally lost the benefits Another key element social interactions. We're social creatures Um, we need to have social interactions and if we don't get them Uh, it damages our health significantly. All right, so we need social engagement But curiously, uh, we don't necessarily need engagement with actual human beings So in some experiments it turns out that if you look at human faces hear human voices If you watch television You watch movies You can uh and train, you know, your brain can be fooled into thinking you're getting social interactions social engagement And you can uh improve your health It's very important that these social interactions happen during the day All of your stressful interaction should be in the daytime In nighttime You want an you don't need to avoid people at night But your nighttime interactions they should be intimate comfortable stress-free All right, so now Often when I give these talks, uh, someone will ask a question. All right. Well, it's the best time to have sex All right, and then what I say as well Uh intimate comfortable Loving sex is great at any time Passionate stressful sex only in the daytime. All right, so Okay, um Now all of these uh daytime and training things you need to concentrate them in the daytime and not do them at night