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What are some of the other biggest myths within exercise that you've come across in writing this book?


Gosh, there are so many, I had to actually limit, limit it to ten. So I think if you want to understand physical activity and exercise, you also.


Have to understand inactivity.


And I think one of the biggest myths out there is that you need 8 hours of sleep a night and that sitting is the new smoking. If you think about those two different myths, why is it that we're constantly told to sleep more and to sit less? Actually, it seems a little contradictory to me, right. And it turns out that let's take sitting first. So there are all these slogans like sitting is the new smoking and it's really bad for you and every time you sit in your chair you lose 2 hours of your life and whatever. Turns out that all animals sit, right? My dog sits, cows sit, chickens sit, every animal sits, and hunter gatherers also sit. In fact, some of my students actually put sensors on hunter gatherers and we're doing some research in farmers as well, but they sit just as much as westerners. So sitting is, there's nothing special about being about today's life. It's that we sit all day long and don't do anything when we're not sitting. Right. And furthermore, the big difference is not.


So much how much we sit, but how we sit. So it turns out that people who, if you get up every once in a while, right, interrupted sitting is actually much more healthy than non interrupted sitting for the same amount of time. So in other words, two people might, in the west people sit for an average about 40 minutes at about. Whereas hunter gatherers for example, or farmers in Africa where we work, get up every about 1015 minutes. And when you do that, it's like turning on the engine of your car, drive it around the block, you're turning on all kinds of cellular mechanisms, you lower blood sugar levels, all kinds of genes get activated and it turns out that that is by far the most important way to sit. So just get up every once in a while, just pee frequently, make a cup of tea, pet your dog, whatever.


Thinking when I'm on planes and I've got a long flight, I always sit.


In the aisle, right? So I can get up a lot. Always.


What about sleep then?


So sleep is another interesting one. So this idea that you need 8 hours of sleep has been around for a long time. It's been around basically since the industrial revolution. But if you actually colleagues in my field, so in evolutionary medicine, have put sensors on people who don't have all the things that we're told have destroyed sleep.


So think about it. We're told that tv and lights and our phones and all these things are preventing us from sleeping. Edison destroyed sleep, right? So when you put sensors on people.


Who don't have any electricity and they don't have tvs and they don't have phones, and they don't have any of these gadgetry, it turns out they sleep like six to 7 hours a night.


And they don't nap.


So this idea that natural human beings sleep 8 hours a night is just nonsense. It's just not true. And furthermore, when you start looking at the data, 7 hours, if you actually.


Look at, if you graph sort of.


How many hours a night you sleep on the x axis and sort of some outcome like cardiovascular disease or just how likely you are to die, it's kind of a ushaped curve. So people who don't get much sleep are in trouble, but the bottom of that curve is pretty much always about 7 hours. So people actually do better if they sleep 7 hours rather than 8 hours. And yet we're told that if you don't sleep 8 hours, there's something wrong, right?


Oh, so you can oversleep.


Well, yeah. I mean, there's also some complexity to.


This, too, because, of course, people who.


Are ill might be sleeping more.


And so there's some biases that creep into how you analyze the data.


But basically it turns out that seven is, for most people, optimal.


But there's a lot of variation, right. Teenagers sleep more, older people sleep less.


It's complicated.


One of the things that popular in culture as well is this idea of doing 10,000 steps a day.


Yeah, now that's fun. That started because of a japanese pedometer. Right before the Olympics were in Tokyo in the 60s, they had invented the pedometer, and they were sitting in a boardroom and they were discussing what to call the pedometer. And they picked out of, just out of the blue, they picked 10,000 steps, because that's apparently an auspicious number. And it sounded about right. There was no science behind it. Interestingly, it turns out it's pretty good.


If you look at steps per day.


And health outcomes, your average hunter gather walks between ten to 18,000 steps.


Depends on male, female, et cetera. And if you look at steps per.


Day and outcomes about around 7000, 8000 steps, the curve kind of bottoms out.


Right. There doesn't seem to be a huge advantage to taking more than that per day in terms of large epidemiological studies.


So it turns out to be not that bad a goal, but it's not a perfect number, like a lot of things, right? It's a reasonable goal to shoot for.


A lot of people exercise because they believe it will help them to lose fat. Belly fat.


One of the biggest debates on the planet.


It has been a huge debate, even on this podcast. I've had multiple people come and say a whole range of things about weight loss and cardio, and I'm kind of, I don't know what to believe anymore.


Well, anybody wasn't confused, doesn't understand what's going on, right? It's sad that there's such a debate.


But that's how science works, right? So, as you know, I wrote about that in this book. Part of the explanation for the debate is that, again, what dose are you analyzing? In what population, in what kind of context, right? So pretty much every major health organization in the world recommends that you get 150 minutes per week of physical activity. That's kind of like the benchmark. That's what the WHO, the World Health Organization considers the division between being sedentary versus active. And a lot of people are unfit and overweight and struggling to be physically active have struggle to get 150 minutes a week, right? So a lot of studies prescribe 150 minutes a week of exercise, walking, for example, or moderate intensity physical activity, and then look at its effects on weight loss. And guess what? When you walk 150 minutes a week, which is what, 20 minutes a day of walking, which is about a mile, a mile a day, you're not going to lose much weight. You're basically burning about 50 calories a day doing that, right? That's a piddling amount of calories compared to drinking a glass of orange juice, right? So surprise, surprise, those kinds of studies show that those doses of physical activity are not very effective for weight loss.


However, plenty of rigorous, controlled studies that look at higher doses of physical activity, 300 minutes a week or more, find that they are effective at losing, for helping people lose weight, but not fast and not large quantities. So you're never going to lose a lot of weight really fast by exercising. It's just not going to happen. Because a cheeseburger has, what, 800, 900 calories, you have to run 15, lose that to burn the same number of calories and you're going to be hungry afterwards, too. So you're going to make some of that back. You have compensation physical activity. There's just no way around it. You have to be a flat earther not to argue this way, but physical activity can help you lose weight, but it's not going to help you lose a lot of weight fast and not at the low doses that often are prescribed. But the one thing that we do agree on, and I think this would not be controversial, is that physical activity is really important for helping people prevent themselves from gaining weight or after a diet, from regaining weight. And there are many, many studies which show this.


One of my favorite was a study that was done in Boston on know, policemen have a reputation, know, having too many donuts and being overweight. Right? And Boston is no exception. So they did this great study at Boston University, right across the river, where they got a bunch of Policemen on a diet, really severe diet. The policemen all lost weight, but some of the policemen had to diet and exercise. Some just dieted alone. And as you might imagine, the ones who dieted plus exercise lost a little bit more weight. Not a lot, just a little. And then they tracked them for months afterwards. Because most people, after a diet, the weight comes just crashing back. Right? The policemen who's kept exercising even after the diet was over, and they went back to eating whatever the hell they wanted. Donuts, whatever. They're the ones who kept the weight off, but the ones who didn't exercise, the weight came crashing back. Another good example would be the, have you ever seen the tv show the biggest loser?


Yes. Where people go on and lose weight?


Yeah. So this crazy show, right? These people, this is totally unhealthy. They were confined to a ranch in Malibu, and these people lost ridiculous amounts of weight. Guy named Kevin hall at the National Institute of Health studied them for years afterwards and looked at, and most of them regained a lot of the weight that they lost. And there was one person on the show who did not, and that was the person who kept exercising. And that's just yet more when you said one data point, but there's lots and lots of evidence to show that physical activity, what its other important benefit when it comes to weight, is preventing weight gain or weight regain. When we talk about dieting, we talk about exercise or diet. Exercise or diet. Like, why is it an or? I mean, why isn't it exercise and diet? Diet is, of course, the bedrock for weight loss. But exercise also plays an important role and should be part of the mix.


On the police example and the biggest loser example, I can relate in the sense that when I exercise, when I go through the moments of my life where I'm most committed to exercise, I'm also most committed to my diet. Yeah, because if I go to the gym, I will not then leave the gym and have a donut or a pizza. Absolutely not. It seems like wasting the effort. So if you look at the sort of correlation between the moments in my life where I eat healthiest, they're also the moments in my life where I'm most focused on the gym. And I noticed there was a couple of months ago, had a bit of a motivation slump, managed to stay in our little WhatsApp group, but coasted down the bottom of the leaderboard for a couple of months on just like, surviving every month by one. And through those moments, my motivation in the gym had gone down and my diet had gone down. The minute I managed to get in the gym and do a big workout the same day, my diet came back.


Yeah, of course. Right? And they covary. Right? And that's one of the reasons why when people do big studies, you can look at what people die of, right? What's on the death certificate? Cancer, heart disease, whatever. Heart attack. And then you look at what caused the cancer, what caused the heart disease. When people try to do that, it's almost impossible to separate diet and exercise, because people who tend to eat better also tend to exercise more. They're both in our modern, upside down, chopsy turvy world. They're both markers of privilege. People have money to go to the gym, also have money to buy healthy foods, and people who care about their physical activity also tend to care about their diet at that level. They're very hard to separate. If you're studying a particular component of a system in a randomized controls trial in a lab, you can separate them out. And so we know that they have independent and also interactive effects. Close.