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

In this moment, Harvard University professor and best-selling author, Daniel Lieberman, busts some of the most common myths around exercise. For 2 of the biggest myths, Daniel says that they are too simplistic, saying that you must sleep 8 hours a night or that sitting is terrible for your health. Instead, he says that most people do better with 7 hours of sleep a night, (but this can change depending on age and health) also, sitting isn’t bad for you if you mix it up with regular interruptions. Daniel also helps to clear up the debate that exercise does nothing for weight loss. He says the problem is actually that the recommended 150 minutes per week of exercise is not nearly enough, but higher levels of exercise lead to sustained weight loss and prevents regaining weight after losing it. In reality he claim that most of the truth about diet and exercise is more complex than we are led to believe. Listen to the full episode here - https://g2ul0.app.link/hIETpSdN5Fb Watch the Episodes On Youtube - https://www.youtube.com/c/%20TheDiaryOfACEO/videos You can purchase Dr Lieberman’s newest book, ‘Exercised: The Science of Physical Activity, Rest and Health’, here: https://amzn.to/49udz2v Learn more about your ad choices. Visit megaphone.fm/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:03Steven Bartlett?

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

• 0:10Speaker 01

  Gosh, there are so many. I had to actually limit it to 10. 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 eight hours of sleep a night, and that sitting is when you're smoking. But basically, 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 when you're 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. Turns out that all animals sit.

• 0:54Speaker 01

  My dog sits, cows sit, chickens sit, every animal sits, and hunter-gatherers also sit. In fact, some of my students actually put censors 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 today's life. It's that we sit all day long and don't do anything when we're not sitting. 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, interrupted sitting is actually much more healthy than non-interrupted sitting for the same amount of time.

• 1:36Speaker 01

  So in other words, 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 10, 15 minutes. And when you do that, it's like turning on the engine of your car, if you're going to 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.

• 2:08Steven Bartlett?

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

• 2:11Speaker 01

  I always sit in the aisle, so I can get up a lot, always.

• 2:15Steven Bartlett?

  What about sleep then?

• 2:17Speaker 01

  So, sleep is another interesting one. So this idea that, you know, that you need eight hours of sleep has been around for a long time. It's been around basically since the Industrial Revolution. But if you actually, so colleagues in my field, so in evolutionary medicine, have put censors on people who don't have, have all the things that we're told have destroyed sleep. So think about it. We're told that TV and lights and, and, you know, our phones and all these things are, are preventing us from sleeping, you know? Edison destroyed sleep, right? So, so when you put censors 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, have any of these gadgetry, right? Electric, you know, they, it turns out, they sleep like six to seven

• 3:00Speaker 01

  hours a night. And they, and they don't nap. So this idea that natural human beings sleep eight hours a night is just, is just nonsense. It'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 U-shaped curve. So people who don't get much sleep are, are 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 yet we're told that if you don't sleep eight hours, there's something wrong, right?

• 3:42Steven Bartlett?

  Oh, so you can oversleep?

• 3:44Speaker 01

  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, there's some biases that creep into the, how you analyze the data. But, but basically, it turns out that seven is, for most people, optimal. But there's a lot of variation, right? You know, teenagers sleep more, older people sleep less. It's complicated.

• 4:03Steven Bartlett?

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

• 4:07Speaker 01

  Yeah. Now, that's fun. You know, that started because of a Japanese pedometer. So, but right before the, the Olympics were in Tokyo in the, in the 60s, they had invented the pedometer. And they were, and 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 act, if you look at, at steps per day... And health outcomes, your average hunter gather walks between 10,000 to 18,000 steps. Depends on male, female, etc.

• 4:48Speaker 01

  And if you look at steps per day and outcomes, about around 7,000 to 8,000 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, you know, large epidemiological studies. So 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.

• 5:15Steven Bartlett?

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

• 5:19Speaker 01

  Ah.

• 5:20Steven Bartlett?

  Belly fat.

• 5:21Speaker 01

  One of the biggest debates on the planet.

• 5:22Steven Bartlett?

  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.

• 5:34Speaker 01

  Well, anybody who wasn't confused doesn't understand what's going on, right? You 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.

• 5:52Speaker 01

  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 WHO, the World Health Organization, considers the, the division between being sedentary versus active.

• 6:21Speaker 01

  So, and a lot of people are unfit and overweight and struggling to be physically active have struggled to get 150 minutes a week, right? So a lot of studies prescribe 150 minutes a week of exercise, walking, for example, a moderate intensity of physical activity, and then look at the 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, which is about a mile, a mile a day.

• 6:47Speaker 01

  You're not going to lose much weight. You're basically burning about fifty calories a day doing that. Right? That's a piddling 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. However, plenty of rigorous controlled studies that look at higher doses of physical activity, three hundred 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, you know, a cheeseburger has what? You know, eight hundred, nine hundred calories.

• 7:29Speaker 01

  You have to run, you know, fifteen 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. So, so physical activity is, is actually, there's just no way around it. You have to be a flat-earther not to argue this way. But there, you know, their, their, 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 policemen.

• 8:12Speaker 01

  You know, policemen are kind of have a reputation for, you know, having too many donuts and being overweight, right? And Boston is no exception. So they did this great study at, at, at Boston University, right? Across this, off 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 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 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.

• 8:58Speaker 01

  The weight came crashing back. Another good example would be the, have you ever seen the TV show The Biggest Loser?

• 9:03Steven Bartlett?

  Uh, yes, where they, where people go on and lose weight.

• 9:05Speaker 01

  Yeah, so that, so that's crazy show, right? These people, you know, this is like totally unhealthy. They were confined to a ranch in Malibu and these guy, these people lost ridiculous amounts of weight. Guy named Kevin Hall at the National Institute of Health studied them for, for, 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, you know, just yet more, once a 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, 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?

• 9:49Speaker 01

  Diet is, of course, the bedrock for weight loss, but exercise also plays an important role and should be part of the mix.

• 9:56Steven Bartlett?

  On the 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.

• 10:11Speaker 01

  Yeah.

• 10:12Steven Bartlett?

  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 in my life where I eat healthiest, they're also the moments in my life where I'm most, most focused on the gym. And I noticed there was a couple of months ago, I had a bit of a motivation slump, managed to stay in our little WhatsApp group, but coasted down the bottom of the leaderboard for, 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. The minute I managed to get in the gym and do a big workout. The same day, my diet came back.

• 10:53Speaker 01

  Yeah, of course, right? And they co vary, right? And 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 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 our 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, topsy turvy world, they'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.

• 11:35Speaker 01

  So so at that level, they're very hard to separate. However, 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.