Science Vs - Weight: Is Fat Unhealthy?

Episode Date: September 16, 2021

We’re hearing nonstop chatter about the “quarantine 15.” But should we really care if we put on weight? Is fat bad for us? We talk to Prof. Henry Blackburn, Assoc. Prof. Laura den Hartigh, and Assoc. Prof. A. Janet Tomiyama.  Here’s a link to our transcript: https://bit.ly/2XxewHo Note: In this episode we discuss weight, weight loss, and weight stigma. Please take care when listening, and here are some resources: U.S. helpline for the National Eating Disorders Association: 800-931-2237 SAMHSA's National Helpline US: 800-662-HELP (4357) National Suicide Prevention Lifeline: 800-273-TALK (8255), or text the Crisis Text Line (text HELLO to 741741).  Find other resources at: spotify.com/resources This episode was produced by Rose Rimler, with help from Michelle Dang, Ekedi Fausther-Keeys, Meryl Horn, and Nick DelRose. We’re edited by Blythe Terrell. Our executive producer is Wendy Zukerman. Fact checking by Diane Kelly. Mix and sound design by Bumi Hidaka. Music written by Bumi Hidaka, Peter Leonard, Emma Munger and Bobby Lord. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hi, I'm Rose Rimler. Wendy Zuckerman will be back soon, but for now, you're stuck with me. And this is Science Versus from Gimlet. This is the show that pits facts against fat. And just a quick note before we begin. This episode is going to talk about weight and weight loss. And if these are sensitive topics for you, please take care while listening. Okay, on with the show. These days, a lot of people are talking about their weight. If you've tried to put on your pre-pandemic jeans, you may find they are a little snug. Doctors are calling it the quarantine 15, and you know what I'm talking about.

The pounds that some people are putting on during the pandemic. One survey of a few thousand Americans found that more than 40% said they gained weight they didn't want to gain during the pandemic. I can relate to this. I've gained weight during the pandemic too. And at first I didn't realize it, probably because I had switched from work pants to loungewear early on in quarantine. But then I went to the doctor and got weighed, and I was surprised to find out I had gained

something like 10 pounds. I plugged my height and my new weight into an online BMI calculator, and it spat out overweight. I had crossed a threshold, and now I was part of a group that includes three out of four Americans. That's how many of us are considered overweight or obese. Gaining the weight kind of kicked off a chain reaction in my brain. I felt bad about myself, guilty, and a little worried. Because we're told that weighing too much, being fat, is incredibly dangerous, that it can skyrocket your risk of tons of diseases and even cut your life short. But when I talked to my friends about all this, they were like, don't worry about it. Ignore the BMI chart because it's bogus. It doesn't mean anything. For one thing,

it doesn't separate fat from muscle and it's super outdated anyway. But is that right? I decided to try to find out. I came into this thinking that the science around health and weight must be pretty settled by now, but I've come to find out that that's far from true. So today on the show, join me and the rest of the team as we go through the weird journey of how the BMI came to be to see if we can actually trust it. And then we'll find out what exactly fat is doing in our body. Is it really hurting us? And is it possible to be fat and fit? When it comes to our pants, you may find they are a little snug, but then there's science. That's coming up after the break. Bumble knows it's hard to start conversations.

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I'm bringing in the A-team. So brace yourselves. Get ready to learn. I'm Jan 11. I'm Steve Strogatz. And this is... Quantum Magazine's podcast, The Joy of Why. New episodes drop every other Thursday, starting February 1st. Welcome back. Today we're looking at whether it really is that bad for your health to be fat.

And a quick note about our words in this episode. A lot of people don't like the words overweight or obese. Some people prefer the term fat as a neutral way to describe a person's body, like tall. But not everyone is comfortable with using fat this way. And meanwhile, overweight and obese both have specific definitions in medicine. So we're going to end up using all these terms, but we'll try to be careful about when and why we use them. Okay, so in order to talk about this at all, we've got to start with the BMI, the body mass index. Every stat you've ever heard about how many Americans are overweight comes from this measure. Hundreds of thousands of

studies rely on it. It's a staple of modern medicine. So where on earth did it come from? To find out, we're going to go back to the 1950s, to the University of Minnesota's football stadium. The Golden Gophers are battling it out in the Big Ten conference. And our story starts down in the depths of the stadium. You enter through gate 27, just as if you had a ticket to gate 27. And then there's a maze of hallways and offices along them under the sloping roof of the bleachers above. This is Henry Blackburn. He's taking us to the lab where the BMI was born.

He's a professor emeritus at Minnesota. So when we worked there on a Saturday, we could hear a distant rumble when the Minnesota team got a touchdown. We would run out and run up the causeway and see if we could see the extra point kick. Sometimes invaded by vermin because of all the food left in the stands and the corridors. But it was our place. We were very much at home there.

And one thing they were doing in this weird lab was trying to answer this big question. How much fat do we have in our bodies? This was important because scientists figured it was the first step in understanding whether fat is bad for us. To get at this, nerds developed these equations to try to estimate whether people had too much fat based on their height and weight. So you could just plug in someone's measurements into the equation and voila, you'd get a sense of how much fat they were

carrying around. But the problem was, these equations hadn't really been tested. No one knew if they were accurate or if one was better than the others. And testing it was hard. How would you do it? You need to get to all that fat in our bodies, the fat that's under the skin and deep inside us. And you have to do it without CT scanners or MRIs because they weren't invented yet. And you have to separate out the stuff that's not fat, like bones and muscles, and... I'll bring up the subject of intestinal air. We're talking about farts is what we're talking about, right?

Yes, exactly. And that's a word I'm not allowed to use in my family. My wife despises that word. It averages about 50 milliliters on average. This is a great piece of trivia, though. 50 milliliters on average of our body is composed of farts. That's right. That's right.

That's less than I might have expected. Depends on your diet. So without fancy modern equipment and with farts getting in the way, how did these nerds measure fat on people's bodies? First, they recruited hundreds of volunteers. 500 normal healthy men of Minneapolis and St. Paul have been serving them as human guinea pigs since 1948. There's some footage of this from a TV special back in the 50s. It shows some white guys in suits and ties heading into a lab where they are led into a special room. Now we're down in the densitometer room.

And it features Henry's boss. He was kind of a big deal at the time, Ansel Keys. And Dr. Keys is about to explain how they measure the weight of a man. Here, let me show you how we get at this. So the way they'd do it was, they'd have this guy stripped down to his underwear, hook him up to a machine that can measure how much air is in his lungs,

and then the main event. The guy is in a metal cage above a tub of water. And then they'd pull a lever, and you'd go underwater. A lever, really? Like, I'm imagining a dunk tank at the county fair. It's exactly a dunk tank, the county fair. It's exactly a dunk tank, except you're lowered in it. You don't splash in it. It's a gentle dunk tank. Yes.

The guy in the footage, whose name is Dick Burlingame, which is the most 50s name ever, he looks surprisingly stone-faced as his head goes lower and lower until he's completely underwater in this cage. He's sitting on a seat that's actually a scale. And once he's underwater completely, he exhales, blowing a big breath out to stop him hovering above the seat. And that's when they record the guy's weight. And the reason they do this is because they want to compare people's weight on land to their weight underwater. And here's why that's important. Say you've got two people who step on a scale and they weigh the same on land.

But one is super muscly and the other one has a lot of fat. When you plop them in the dunk tank, the person with all the fat will weigh less because fat is less dense than muscle. So it kind of floats. From that, knowing the density of the usual density of bone, the usual density of muscle, the density of body water, and density of body fat, you can read off on a chart the percent of body fat.

So with the dunking, and with what we already know about how dense different parts of our body are, they could estimate how much of a person was fat and how much was other stuff. Now they had the data to finally test those untested equations that we told you about, to see which one was the best at predicting how much body fat people actually have. So the team took all this data of people's fat and their height and weight, they put it on a graph as little dot points. They added other data too, measured in a different way from men around the world. And while the group was mostly white,

it did include some men from Japan and Bantu men from South Africa. So all in all, it was about 7,000 men. And they crunched all this data and then in 1972 published their results. The best equation turned out to be... Weight divided by the height squared. Yep, the equation you know and probably hate. And Ansel Keys dubbed it the body mass index. Why didn't he name it after himself? He could have renamed it the Keys quotient, for example. Oh, well, he wasn't Donald Trump. I mean, you didn't have to see his name on every building in town. I'm sorry, I shouldn't have gotten political. We forgive you, Henry. Anyway, from here, the BMI totally blew up. Other groups like the National Institutes of Health and the World Health Organization took the BMI ball and ran with it. They started using it to make the categories that Organization took the BMI ball and ran with it.

They started using it to make the categories that we know today, including overweight and obese. The ramifications of this are huge. When you hear about the obesity epidemic on the news or stats about how unhealthy it is to be fat, chances are that's based on the BMI. But we also hear all kinds of stuff about how the BMI has problems. And what's funny is that even Ancel Keys knew the BMI wasn't perfectly measuring fat. He didn't say it was very good, but he said it was at least as good and a little bit better than all the other indices. If you were to give it a grade, like an A to an F for how well it could estimate body fatness, what grade would you give it? A C, and the others would get D.

A C? Not acceptable in this household. And one of the reasons it gets such a middling grade is this. These days, scientists have fancier techniques than dunk machines to measure how much fat people have. High-tech scanners and MRIs. And what they find is surprising. The BMI usually underestimates fat percentage. Yeah, so we might have more body fat than we would expect given our BMI. And the reason this surprised me is that one of the biggest criticisms you hear of the

BMI is that it doesn't account for muscle. So it might be putting really muscular people in the wrong category. But it turns out it's more likely to be doing the opposite. So that's all about how well the BMI predicts our body fat. But how well does it predict our health? If, like me, you got a stamp of overweight or obese from your doctor, thanks to the BMI, how worried should you be? Well, it turns out this whole area of science is a minefield. There is so much nuance and controversy here that I ended up spending months diving into the literature and talking to scientists. I'm really excited to talk to you because I have so many questions about this.

Okay. I visited a body composition lab. We're looking at like a big kind of industrial scale. This is an industrial scale. We can weigh persons up to 1,000 pounds. And stumbled into a huge science fight. Their stuff is rubbish. It's ludicrous.

It's obviously wrong. For some people, it's more like the bogus mass index. It's crude. It is crude. We're asking it to do much more than it's supposed to be. Okay, so not everything is this controversial. Here's what basically everyone agrees on. People with high BMIs are more likely to have health problems like heart disease, type 2 diabetes, and some kinds of cancer. And they're more likely to have trouble moving around. Plus, people at either end of the BMI spectrum, the extremes of underweight or severely obese, are more likely to die younger compared with people in the middle. But here's where things get muddy. When we look at the less extreme cases,

like being overweight, some studies find that you may actually be less likely to die. Yeah, maybe that little bit of cushioning is doing you some good. But then other studies don't find that. So it's kind of a hot mess. On top of that, the BMI categories were made partly based on studies of disease risk in mostly white people. And things could look different if you're not white. Like one study found that on average, black women with a high BMI tend to be healthier compared to white and Hispanic people. The thing is, when scientists created these categories of overweight or obese, they were kind of making bright lines around at risk of disease, not at risk, healthy, unhealthy. And the BMI really isn't that good at doing that. Like one of the most confusing things that we see

is that some people categorized as obese don't have any health problems at all. For example, one study of 40,000 people found that 30% of those whose BMI said they were obese had perfectly healthy blood pressure, blood sugar, cholesterol levels, and that kind of thing. Sure, some of those people will go on to develop these problems, but there are plenty of people who stay healthy the whole time scientists are watching them. So what's up with this? Is it really possible to be fat and fit? That's coming up after the break. Welcome back. We've just learned that this idea we have in our heads that being overweight equals unhealthy isn't quite right.

In fact, when you get down and dirty in the data, it's super messy. So how is that possible? Can some fat be good? I guess I'm fascinated by fat because it's so overlooked, you know? This is Laura Denhartig. She's an associate professor at the University of Washington who studies fat. And she told us that by overlooking and underappreciating fat, we're missing a big piece of the puzzle. Because here's what you got to know. Not all fat is created equal. There are different kinds.

Let's start with the stuff that's under our skin. Yes, yes. So that's like the fat in your legs and the fat in your butt and in your arms. Scientists call it subcutaneous fat. We're going to call it cute fat. Get it? Subcutaneous fat. We're going to call it cute fat. Get it? Sub-cute-aneous? And right off the bat, we're going to tell you,

it's not thought to be dangerous. I think what we need to do is embrace our inner, like, cherub. You know, like all those old, old art paintings of the really fat women who are just hanging out, appreciating their cellulite. You know, that's beautiful. It's healthy fat. Yeah, even though this fat is kind of You know, that's beautiful. It's healthy fat. Yeah, even though this fat is kind of hated on, it's actually doing some good work.

One of the things it does is put away energy for future use, which, honestly, think about it. That is cool. If we didn't have fat, we'd have to constantly be eating to get energy. Laura talked to producer Meryl Horn about it. There are pockets of fat in our bodies that are always supposed to be there. You know, they're called depots.

So like the wiggly part of your forearm or the top of your arm, things like that. They're always there. The little arm jiggle. That's also a good part. That's like a fat depot. Yeah, I would consider it a good part. That's like doing its job. Yep.

And its job isn't just to quietly sit around storing energy for a rainy day. Scientists used to think this, that fat just sat there, but they've discovered that it's actually constantly doing work. Like what's kind of amazing is that fat uses chemical signals to communicate with the brain. There's signals directly to the brain that will tell us what our energy status is. So there's this really tight link between these hormones coming from fat in a healthy way and to the brain that will tell us what our energy status is. So there's this really tight link between these hormones coming from fat in a healthy way and to the brain, and it's constantly moving. Like our fat cells make a hormone called leptin that travels to the brain and basically tells our brain how much fat our body has, letting the brain know we're good. We're not wasting away.

And this hormone made from our fat, it even helps us learn and remember things. So that all makes fat sound pretty good. So why are we worried about fat? To be honest, I think fat is pretty good. But there are times when fat is not pretty good. And that's when it weasels its way into other parts of our body, away from those pockets under our skin. This is called visceral fat. And when this shows up, that's when things get not so cute. So this fat is also, you know, right in our abdominal region, and it surrounds our internal organs. It surrounds our liver, it gets into our liver, it surrounds our heart, our pancreas. This particular type of fat,

this visceral fat, is really bad for us. Yeah, this kind of fat is kind of the evil twin of all that healthy fat we were just talking about. Bizarrely, even though it's basically the same stuff as the cute fat, it behaves a lot differently. Like Laura says, it spits out a different mix of chemicals than the other stuff. It makes a lot more inflammation. So inflammation is like proteins that signal that there's a problem. And visceral fat makes more of those signals. And those signals can eventually lead to big problems like diabetes and cardiovascular disease. Let's zoom in on the liver. This type of fat can be really bad for the liver, and here's

why. A healthy liver helps control how much sugar is in our blood. If there's too much, the liver will pull some of it out. But the chemical messages and other stuff coming from visceral fat can mess this whole thing up, and that can make it easier for sugar to build up in our blood, which makes it more likely that we'll get diabetes. Even when it comes to our old nemesis COVID-19, scientists are now finding that it may be visceral fat, not cute fat, that ups the risk of getting really sick. All of this could help explain why the link between BMI and our health isn't a straight shot. Remember how we told you that it's possible that almost a third of people classified as obese are perfectly healthy? Well, some studies find that people in this group tend to have more cute fat than visceral fat.

Okay, but how do we know if we're packing the cute fat or the bad stuff? Without a CT scanner, a crude measure is to think about your body shape. Are you an apple or a pear? Seriously, these are terms that actually show up in science. It's so funny to me, all this, what I've been reading in the scientific literature, it's like apple-shaped, pear-shaped. I'm like, this reminds me of Cosmo when I was a teenager. And it'd be like, what swimsuit should you pick?

Which is, pick your silhouette. Are you an apple or are you a pear? It is really outdated, I know, I know. I can't stand it, but it is quite accurate. People who are apples tend to put weight on around their waist, and this means that they tend to have more of that bad visceral fat. The pear-shaped folks have more narrow waist and bigger hips and butts, which can translate to less of the bad stuff. Is there anything we can do about that? Oh gosh, I wish there was. So the shape of your

body is almost purely genetic. You know, where you're going to put your body fat down is largely based on your genetics and some environmental factors too. There's nothing you can do to change the shape of your body. But Laura told us that if you do lose weight, you'll probably lose some visceral fat. The probably most common way to get too much fat in your liver is to have too much fat in your body in general. And if we have too much fat, some is undoubtedly going to spill over. But if you lose any fat, you'll lose some visceral fat. And that has tremendous health benefits, just losing a little bit of it. Also, studies show that doing really vigorous exercise, even if it doesn't make you lose weight, can tamp down visceral fat.

Okay, bottom line here. Fat isn't always harmful, but it can be, especially when it starts hanging out in places we don't want it, around our organs. And people who are fatter are likely to have more of this dangerous kind of fat. And that can be one reason why having severe obesity increases your chances of getting certain diseases. But it might not just be the bad fat spewing out the bad chemicals that's to blame for this. There's some new research coming out suggesting the crappy way fat people are often treated could also be making them sick. In general, how are higher weight people treated differently from lower weight people? Wow, well, how long do you have to talk

on this podcast? This is A. Janet Tomiyama, an associate professor of psychology at UCLA. She told us that you see this bias everywhere. Fatter people are less likely to get hired for jobs and make less money than thinner people for the same work. It starts so early. In one study of preschoolers, two-thirds of the little sh** didn't want to invite heavier kids to their birthday party. And research is showing that shaming people about weight issues, it's not just mean, it's actually affecting people's health. If you experience weight discrimination, you're at greater risk of dying earlier. And this isn't about how much you weigh. It's about how much crap you get for your weight

that's doing the damage. So it doesn't matter if you are, you know, a skinny mini person or somebody who has a really large body. She told us about an analysis of thousands of people, mostly over 40, who were asked about whether they'd been discriminated against or shamed for their weight. Five to 10 years later, they found that people who experienced weight discrimination were at least 30% more likely to have died. And that was after controlling for BMI and underlying diseases, which suggests it's about the stigma, not the weight itself. Another study found that getting discriminated against because of your weight was linked to heart disease and stomach ulcers. And again, that was after controlling for BMI. So what's going on here?

How could being hassled for your weight be bad for your health and even kill you? One thing that can be happening, Janet says, is that this kind of stigma can bump up your stress hormones. She's actually done studies where she has people get stressed about their weight and then measured their levels of the stress hormone cortisol, and she finds that it goes up. If your cortisol is constantly buzzing, that's bad for you. It's thought to raise your risk of stuff like heart disease. And cortisol can also make you gain more of that bad kind of fat, visceral fat.

So given that we see correlations between fatness and heart disease, how do we know what's from the fat and what's from the stigma? If you had to guess what percentage of these health problems are caused by the weight itself versus social reasons, could you guess a percentage? I don't know that I could speculate on that, but it's not zero and it's been treated like it's zero.

And it's not just your body's biological reaction to fat shaming that might make you sick, but studies have shown that doctors have anti-fat bias too. In one survey of 400 doctors, almost 20% admitted that they disliked or were disgusted by obese patients. Studies have found that patients are picking up on this. They're like, yeah, I can tell. And they tell researchers that doctors are crappy to them, which makes them not want to go in. One person we reached out to said that she was afraid to go to the doctor because of this. We also hear stories of doctors being so focused on a patient's weight that they totally miss serious health problems. Like Janet told us about this one woman named Rebecca. The initial symptom that made her go to the doctor was that she was having trouble breathing.

And several physicians attributed her difficulty breathing to her body mass index. They said, you're obese. That's why you can't breathe. You need to lose some weight. Come back later. And in actuality, what Rebecca had was lung cancer. Oof. That's really terrifying. It is. Okay, so where does this leave us? Well, for people with higher BMIs, we do see an increase in some conditions, like diabetes and some cancers and mobility problems. But this is far from

universal. Lots of fatter people are perfectly healthy. And of course, some skinnier people are unhealthy. A few scientists told me that it's best to think of a high BMI as just one risk factor, not the be-all end-all. Generally though, if we could wave a magic wand and make everyone on earth a normal BMI, we probably would be healthier.

The problem is, Harry Potter has been cancelled. There is no magic wand. And weight loss is super hard. In fact, only something like one in five people who tries to lose weight can lose it and keep it off. So given that, it probably makes more sense to stop obsessing over the scale and pay more attention to our behaviors, what we're eating and how much we're moving. For example, one Dutch study followed overweight and obese people for 15 years and found that those who got lots of exercise

had no increased heart disease risk. And a bunch of other studies find similar things, that healthy behaviors cut down on lots of problems, regardless of BMI. For me personally, all this made me realize there was no reason to freak out when I crossed over into this overweight category. It's not like I'd accidentally stumbled into the upside down

with a demogorgon out to get me. Although it was disappointing to find out it probably wasn't all muscle, but I'm happy with where I'm at now. That's Science Versus. Hello. Hello. Ready, Freddie Akedi? That's the first time anyone's called me that. Akedi Foster-Keys, our intern here at Science Versus. And how many citations are in this week's episode? There are 140 citations in this week's episode.

Okay, that's not too shabby. If people want to go and check them out, where should they go? They can go to the transcript, which is in our show notes. Thanks, Akedi. Thanks, bye. Next week, we're looking at childbirth.

Are doctors interfering too much? Is it over-medicalized? And would most of us be better off with no doctors around at all? She was just like in this euphoric trance. She was butt naked the entire time. It gives me chills thinking about it. This episode was produced by me, Rose Rimler, with help from Michelle Dang, Aketi Foster-Keys, Meryl Horn, and Nick Delrose. We're edited by Blythe Terrell.

Our executive producer is Wendy Zuckerman. Fact-checking by Diane Kelly. Mix and sound design by Bumi Hidaka. Music written by Bumi Hidaka, Peter Leonard, Emma Munger, and Bobby Lord. Thanks to all the researchers we got in touch with for this episode, including Dr. Michelle Foster, Dr. Catherine Flegel, Professor Dimna Gallagher, Dr. Sarah Tracy,

Professor Peter Nilsen, Professor James Stubbs, Dr. Jennifer Kearns, Dr. Fatima Cody-Stanford, Professor Mercedes Carnethon, Dr. Jane Winter, Dr. Haley Banach, Professor Francesco Rubino, And special thanks to Diana Apong and Lila Byers. See you next time.