Moment 143: This Is Why You Can't Lose Weight: Daniel Lieberman

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0:33What 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 it to 10. So I think if you 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 eight hours of sleep a night, and that sitting is the new smoking. You know, that basically, and 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.

1:12So you know, there are all these slogans like sitting at the new smoking, and it's really bad for you. And every time you sit in your chair, you lose two hours of your life, and whatever, it turns out that all animals sit, right? My dog sits, cows sit, chickens sit, every animal sits, and hunter -gatherers also sit. In fact, if you, some of my students actually put sensors on hunter -gatherers, and when 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 sitting, it's that we sit all day long and don't do anything when we're not sitting, right?

1:47So if you, and furthermore, the big distance 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, for interrupted sitting is actually much more healthy than non -interrupted sitting for the same amount of time. So in others, two people might, in the West, people sit for an average about 40 minutes at about, whereas hunter -gatherers, for example, are farmers in Africa where we were get up every about 10, 15 minutes. And when you do that, you actually, it's like turning on the engine of your car, you don't drive it around the block.

2:22You'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. I think thinking when I'm on planes and I've got a long fly. Yeah, 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 there's an idea that you need eight hours of sleep has been around for a long time. It's been around basically since the Industrial Revolution.

2:58But if you actually, so colleagues in my field, so an evolutionary medicine, that put sensors on people who don't have all the things that were 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, right? It turns out they sleep like six to seven hours a night and they don't nap. So this idea that natural human being sleep eight hours a night is just nonsense.

3:40It's just not true. And furthermore, when you start looking at the data, seven 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, you know, some outcome like cardiovascular disease or just how likely you are to die, it's kind of a ushaped curve. So people don't get much sleep or in trouble. But the bottom of that curve is pretty much always about seven hours. So people actually do better if they sleep seven hours rather than eight hours and get what we're told that if you don't sleep eight hours, there's something wrong, right? Also, you can over sleep.

4:15Well, 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 from most people optimal, but there's a lot of variation, right? You know, 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. You know, that started because of a Japanese pedometer. So right before the Olympics were in Tokyo in the 60s, they had invented a pedometer and they were sitting in a boardroom and they were discussing what to call the pedometer.

4:52And they picked out of just out of the blue, they picked 10 ,000 steps because that's apparently in a spicious 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 10 to 18 ,000 steps, depends on male, female, et cetera. And if you look at steps per day and outcomes, about around 7 to 8 ,000 steps, the curve kind of bottoms out, right? There's that doesn't seem to be huge advantage to taking more than that per day in terms of, you know, large epidemiological studies.

5:34So it turns out to be not that bad a goal, but it's not a, there's no, it's not a perfect number like a lot of things, right? It's just a kind of a, it's a reasonable, it's a reasonable goal to shoot for. A lot of people exercise because they believe it will help them to lose fat. Ah, belly fat. 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 who wasn't confused doesn't understand what's going on, right?

6:07You know, it's, it's sad that there's such a debate, but, 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 and what population in what kind of context, right? So the, 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, you know, the WHA, WHO, the World Health Organization considers the, the division between being sedentary versus active. So and a lot of people are unfit and overweight and struggling to be physically active.

6:56I have struggled 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 effects on weight loss. And guess what? When you, when you walk 150 minutes a week, which is what, 20 minutes a day of walking, it's 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 pittling amount of calories compared to drinking a glass of orange juice, right? So, so surprise, surprise, those kinds of studies show that those doses of physical activity are not very effective for weight loss.

7:37However, plenty of rigorous controlled studies that look at higher doses of physical activity, 300 minutes a week or more, find that they are effective for 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, you know, a cheeseburger has what, you know, 800, 900 calories, you have to run, you know, 15 kilometers to lose that, to burn the same number of calories. You're going to be hungry afterwards too, so you're going to make some of that back. You have compensation.

8:10So, so physical activity is a, is actually, there's just no way around it. You have to be a flat earth or not to argue this way, but the, you know, the 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. There are many, many studies would show this. One of my favorite was a study that was done in Boston on policemen, you know, policemen are kind of a reputation for, you know, having too many donuts and being overweight, right?

8:47And Boston is no exception. So they did this great study at Boston University, right across, across the river, where they got a bunch of policemen on a diet, a really severe diet, the policemen all lost weight, but some of the policemen were, were 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. But, and then they tracked them from 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.

9:25But 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 they were people going on these weight. Yeah, so there's crazy show, right? These people, you know, this is like totally unhealthy. They were confined to a ranch and Malibu, and these got, these people lost ridiculous amounts of weight. Guy named Kevin Hall of 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.

10:00And that's, you know, just yet more, when he said one data point. But there's lots and lots of evidence to show that physical activity, what it's other important benefit when it comes to weight is, 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 young police example and the Biggest Loser example, I can relate in the sense that when I exercise, when I go through the, the moments of my life where I'm most committed to exercise, I'm also most committed to my diet.

10:41Yeah. Because I, 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 of my life where I eat healthy is, they're also the moments of 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 a, 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.

11:17The minute I managed to get in the gym and do a big workout, the same day my diet came back. Yeah, of course. Right. They co -vary, right? And that's one of the reasons why when people do big studies of, of you know, what, you know, you can look at what, what, what people die of, right? What's on the death certificate? You know, cancer, heart disease, whatever, heart attack. And then you look at what caused the cancer, what caused 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, Trapsy Turvy world.

11:54They're both markers of privilege. People have money to go to the gym, also have money to buy healthy foods. And, and people who care about their physical activity also tend to care about their diet. So, so at that level, they're very hard to separate. However, if you're studying a particular component of a system and a randomized controls trial and a lab, you can separate them out. And so we know that they have independent and also interactive effects.