Does Your DNA Determine Your Weight?

MAUGHAN: Shockingly, a lot of people walking down the street do think like, “Whoa, is that Tom Brady?”

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DUCKWORTH: I’m Angela Duckworth.

MAUGHAN: I’m Mike Maughan.

DUCKWORTH + MAUGHAN: And you’re listening to No Stupid Questions.

Today on the show: is obesity a matter of nature or nurture?

DUCKWORTH: Wow, we’ve just got, like, a gajillion genes and got a gajillion experiences.

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MAUGHAN: Angela, I’m so excited to talk to you about today’s question, because it is about something that is, I think, kind of taking over the cultural zeitgeist right now.

DUCKWORTH: Ooh. And what would that be? Taylor Swift?

MAUGHAN: It is about this new Wegovy/Ozempic craze, which maybe you’ve heard about. There are all these people using it to lose lots of weight.

DUCKWORTH: Yes, I have heard of this “miracle drug.”

MAUGHAN: Well, so here’s the deal. It’s sort of changing the face of obesity, because obesity has generally been viewed as an issue of, like, personal responsibility — you don’t move enough, you don’t eat right, stuff like that.

DUCKWORTH: Right, I remember seeing these headlines like, “This new drug shows that it’s not willpower, that really we should think about weight as a medical condition, and it’s not behavior or motivation.”

MAUGHAN: Yeah, so the idea is that for some people, it’s extremely difficult to lose weight, probably because of their biology. They maybe have this set point that’s naturally higher, and this medication helps shift that set point. I mean, I’ve always dealt with weight fluctuation, and it made me curious to know where my natural set point is, or what I can do to change it. So look, is my weight totally genetic? Or how much does my behavior matter if my biology wants me to be a certain way? What control do I have over weight versus what control does biology have over my weight?

DUCKWORTH: I love this question, Mike, in part because the nature/nurture question — like, how much of who I am is genetic? How much is it that I was born this way? And how much of it is nurture, like, my experiences and my free will? This isn’t just about obesity and weight. This is about personality, and character, and intelligence, and you could even argue that this is about every aspect of who we are.

MAUGHAN: When it comes to weight though, I sort of hate the idea that I’m not responsible for it.

DUCKWORTH: You hate the idea that you’re not responsible for it?

MAUGHAN: Right. Like, I want to be able to say that I can change it. The reality is I should move more, I should exercise more, I should make better choices. I like the idea that I can control my own life. But I also like the idea that, oh, well, I guess no matter what I do, I can blame my genes. You know, I have a dear friend who eats whatever they want and will always remain so skinny and that person hates that they’re so skinny and they want to gain weight. So, obviously —

DUCKWORTH: You’re ambivalent, because on one hand, in a way, being exonerated from weight issues by your genetic — you know, the deck of cards that you were dealt, the idea is that, oh wow, that kinda lets me off the hook. On the other hand, I think you have an uncanny instinct for any idea that is going to enhance your sense of agency. And that, by the way, Mike, has not gone up and down over the, whatever, 10 years that I’ve known you. You really like to have an internal locus of control. You lean very hard into, like, “Well, what can I do about this?” I think all of us have that. I mean, all of us want to be forgiven our sins or let off the hook for them, and also have a, an instinct that we should probably take responsibility. And I think the science on nature/nurture is going to be helpful, but it’s not going to be helpful in, like, in a bumper sticker way. People so often want, like, “Well, which is it, nature or nurture?” Like, A or B? And if they’re willing to handle a little bit of nuance, they’re like, “Okay, fine. 70 percent, 30 percent —”

MAUGHAN: Well, right. That’s what was going to go to, because don’t most studies show that it is more nature than nurture, but nurture is how you maximize within the range that you can change? Is that accurate, or no?

DUCKWORTH: It’s a problem in how you phrase the question. So, this question of nature/nurture goes back a long time, at least to the mid-19th century when people like Charles Darwin and his cousin Francis Galton wondered, like, why do people turn out the way they do? And why is one leopard faster than another leopard? But also why are, like, leopards faster than, you know, aardvarks or something. Like, so, of course, Darwin and others of that time didn’t have modern genetics. So, I’ll fast forward you to modern times and 2023. The research on this goes under the title of “behavioral genetics.” So, behavioral genetics is the study of how genetics influences our psychological development. And the first thing I want to tell you is what’s often called “the first law of behavioral genetics.” And that was a phrase coined by Eric Turkheimer, who’s a leading scholar in this field. And I’ll quote him so that I don’t get it wrong. So, the first law of behavioral genetics is that, “all human behavioral traits are heritable.”

MAUGHAN: Not just, like, height, eye color, size of your feet — whatever, right? It’s my personality? Whether I —

DUCKWORTH: Everything! I mean, we have 23 pairs of chromosomes, right? We have DNA, and those chromosomes have a code. And everything about you has to, in some way, be genetic in the sense that your DNA are, like, coding for certain proteins, and that’s why you were born a human and not an aardvark. And my genes being different from your genes, Mike, are partly why I’m me and you’re you. So, when Turkheimer says that the first law of behavioral genetics is that “all human behavioral traits are heritable,” you can by extension just with common sense, think, “Oh yeah, all traits are heritable.”

MAUGHAN: It’s so mind blowing, because if you think about, oh, I’m a happy person, I’m a grateful person, I’m a motivated person, I’m a hardworking person — all of those things are things that you can work on. And I hate the idea that, like, I am inherently either grateful or ungrateful. I am either happy or unhappy. But I think what you’re saying is there is maybe a baseline. Like, I know some people — I have this, I call him my new life coach, he’s not officially, but this guy, Vinny. He’s the happiest person — he’s just happy. I feel like every time I see him, it’s a little bit like a puppy dog. And, like, he makes me happy, because he’s so happy. I think that’s probably inborn in him.

DUCKWORTH: When you describe Vinny, I think of my daughter Lucy. You know my kids, and Lucy is just sunshine personified. You know, one day she was like, “Mom, it’s 72 degrees.” And I was like, “Yeah, I know.” She’s like, “Isn’t that a great temperature?” And I was like, “Oh my God. Who dealt you these dispositional cards?” So, I know what you mean when you meet people and they seem to be naturally extroverted, or naturally confident, or naturally gritty. And when you then hear the first law of behavioral genetics is that all traits are heritable, it does make you think, “Oh, okay, so much is inborn.” But, let me explain further what Turkheimer, if he were in this conversation, I think, would want to impress people with. And that is that: “human development is fundamentally non-linear and interactive.” And that is another quote from Turkheimer. So, let me unpack it: “human development is fundamentally non-linear and interactive.” Okay. So, you are conceived when the sperm and the egg come together, and there’s a little genetic deck that’s dealt. And from that moment on, there are these extraordinarily complex, almost computationally infinite interactions that happen between genes, and between genes and environmental influences. And it’s, like, everything. Like, your mom’s blood sugar on a certain day. And when you are born, who holds you first, and then who your first grade teacher is, and who you get sat next to, and whether you trip and skin your knee in sixth grade and whether your parents take you to Spain or don’t take you to Spain. So, there’s just an uncountable number of environmental influences that interact with all of these genes that you got dealt. And one of the things that is, um, really hard to even wrap a human mind around — I have found it hard to wrap my mind around — it’s just that because there’s this soup of genes that you got and this uncountable number of environmental influences, and each gene and each environmental influence probably has a teeny-tiny effect, but these effects are, like, not just additive. They’re, like, interacting with each other. It’s like, “Oh, and then this happened, and then because this happened, something else is going to happen.” That’s what Turkheimer means by it being “non-linear and interactive.” It’s like the weather. You know, like you’ve ever heard that expression that a butterfly flaps its wings in Houston and there’s a, you know, tornado in Honduras. It’s basically a similar — not exactly the same — intuition. But, like, one event among many will influence this long-term outcome because of all the things that it sets off.

MAUGHAN: I mean, if you’re — we just went to children for a minute. There’s been for years, this big debate on breastfeeding or using formula and all these people are like, “Guess what? Like, I’m just trying to survive. I just had a baby. How about you back off and stop telling me how to feed my child.” It’s enough to almost drive you crazy if you think about it in too micro a level.

DUCKWORTH: Yeah, I mean, it’s true. When it’s hard, people tend just to shut down, and they’re like, “Is it nature or nurture?” or “how much is nature and how much is nurture?” Neither of those phrasings actually make sense when you really understand how genetics work. So when Turkheimer says, look, the first law of behavioral genetics is that everything is to some extent heritable, he’s not saying it’s fixed. He’s not saying it’s — genes are destiny. In fact, he’s saying the opposite, that “development is non-linear and interactive.” It’s so gosh-darn complicated. There’s nothing about you that’s easy to explain. I mean, almost nothing. Eye color is an extraordinarily common thing that people think is genetic. And we — at least I — in elementary school, was assigned the family tree homework. Did you ever have to do this where you have to like, make a family tree of who’s blue-eyed and who’s brown-eyed?

MAUGHAN: I don’t know if I had to do it with eye color, but I’ve certainly made many a family tree.

DUCKWORTH: For a school assignment?

MAUGHAN: Well, yes, for school. I don’t often sit home on Friday night and make family trees just for fun.

DUCKWORTH: Well, by the way, when you’re Chinese, the whole family tree thing where you’re like, “please identify the eye color of your grandparents and your great” — I was like, easy, cheesy, lemon squeezy: brown! But I bring up, you know, eye color because when we were in elementary school — at least when I was in elementary school — I was taught that genes worked in this very simple way. Like, if your mom has blue eyes and your dad has blue eyes, then you’ll have blue eyes and, then, you know, you draw these little charts.

MAUGHAN: Right, you make the little, like, quadrant, and it’s the dominant or recessive gene and you just do your — yes.

DUCKWORTH: Turns out that even things like eye color have, I think, more than a dozen different genes. So, it’s, like, not what they teach in fourth grade. Hundreds of different genes influence your disposition to be heavier or lighter. Every aspect of your genetic makeup, which is super complicated, and every aspect of your experience, which is super complicated, they’re all interacting. And, so yeah, everything is genetic or heritable in some sense, but the reason why you can do something about your weight, and your grit, and your extroversion, and your honesty is because development unfolds in that complicated way.

Still to come on No Stupid Questions: Mike and Angela wonder if better understanding of genetics can help counter fat-shaming.

DUCKWORTH: There’s so much I’ll never know about your DNA.

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Now, back to Mike and Angela’s conversation about how nature and nurture shape your identity.

MAUGHAN: I think it’s amazing when we see how much change has been happening in the world as a whole. And that leads to this question of nature, nurture, all these things, right? I mean, when you look at just the obesity statistics, the worldwide prevalence of obesity has nearly tripled between 1975 and 2016, which obviously is not just because everyone’s genes suddenly changed. That would speak to sort of these environmental or, or behavioral things that have come with it. And there’s a lot to be said about the damage done by weight stigma or weight bias where people who are overweight deal with a lot of negative verbal commentaries, teasing, physical assault, eye-rolling, et cetera.

DUCKWORTH: You know, I think there’s a dimension of this that’s super interesting called “genetic essentialism.” What the idea is, is that we as human beings have a tendency, quote, “to infer a person’s characteristics and behaviors as based on their perceived genetic makeup.” And there are two scientists who have made this observation, and their names are Ilan Dar-Nimrod, who’s now professor at the University of Sydney in psychology, and Steve Heine, who’s a professor of psychology at University of British Columbia. So, let me give you a little quiz, Mike. They have this scale called the Genetic Essentialist Tendency Scale. And I won’t read you all of the items, um, but as I read you a statement, just tell me whether you disagree or agree. “Even in an environment which encourages and nurtures creative behavior, a person without a genetic predisposition for creativity will still be uncreative.”

MAUGHAN: Oh, I disagree with that.

 DUCKWORTH: Okay. “An individual’s particular behavior is not changeable if it has a genetic basis.”

MAUGHAN: Strongly disagree. I hate that idea.

DUCKWORTH: And finally, most relevant to Ozempic and this conversation about fat genes and what we can do about them: “A person with a genetic predisposition for obesity is destined to be fat.”

MAUGHAN: Uh, I’m going to disagree. I mean, I think that obviously the likelihood is higher, but I think you’re not destined to be.

DUCKWORTH: Okay. It’s clear to me that you recognize this tendency toward genetic essentialism, but you counter it in yourself, right? You’re like, “I know it’s not that simple.”

MAUGHAN: Where I want to be careful here, though, is that some people have genes that probably — you’ll tell me if I’m wrong — are so, maybe, extreme on one end of the scale or another that I have some friends who never lift weights and are incredibly strong and toned and whatever, right? There’s extremities on both ends where someone’s genes are so potentially extreme on weight gain, or weight loss, or obesity, or whatnot, that there is probably very little you can do. But most people, I would imagine, fall within a range where there is at least more control.

DUCKWORTH: So, you’re thinking that for most people they fall somewhere in between, but for the extremes, maybe those are kind of like genetic anomalies, right?

MAUGHAN: I would assume so. I mean, what I don’t want to do is say — because, I think it is very dangerous, this whole idea of weight shaming, weight stigma, weight bias. And I don’t want to say that someone who’s on maybe a more extreme end — I’m not going to put all the responsibility on their head. And I don’t think the science would tell us that, right?

DUCKWORTH: Well, you know, the first law of behavioral genetics should prevent us from saying that things are, you know, like, totally under the control of your decisions. Because if it’s true that all traits are genetically influenced, they’re heritable, then you’re exactly right that, like, it is a deck of cards. And some of us inherit hands with a lot of aces, kings, and queens. And some of us are like, “So what do I do this, like, two of clubs?” But one of the reasons I got into the complexity just now is that when it’s a lot of genes that influence one of your traits, it’s less likely that you can point to your really muscular friend and say like, “It’s just genes,” because that really suggests that like he inherited a deck of many, many, many, many genes that were all tilting in the same way. And again, I’m not saying there aren’t people who aren’t genetically lucky and genetically unlucky — and you’re so right, that should help us not stigmatize. But just because they’re on the extreme doesn’t mean it’s genetic. It could be that there are environmental reasons that that person is in the extreme of the distribution. But it’s not our first thought, and I’m as guilty as anyone else. When I see somebody who’s — like Lucy, I’m like, “Oh my gosh, what did you do to win the genetic lottery in happiness?” And I forget for a moment that behavior and development are these fundamentally, like, non-linear and interactive processes. And I can’t say, “Oh, she just got ‘yes, yes, yes, yes, yes’ on all the genes for happiness.” It absolutely could be some path-dependent development where, yes, her genes, but also her experiences, and her experiences interacting with her genes, and her genes interacting with each other, and so on, like that produced this happy disposition.

MAUGHAN: Yeah, look, I think it’s amazing, and there’s so much being said right now obviously in this conversation about genetic essentialism, nature, and nurture — not nature or nurture. But, you know, we started this conversation out talking about weight loss. So look, we would both love to hear from our listeners about your experience with weight loss. Do you think that your genetics made it harder? What, what would you modify about your situation? So record in a quiet place with your mouth close to the phone and email it to NSQ@freakonomics.com. And maybe we’ll play it on a future episode of the show. I’d love to share with you a little story about Bill Maher, who is a late night host, and James Corden, also a late night television host, recently retired. But back in September of 2019, Bill Maher on his H.B.O. show talked about fat shaming. And he basically said, “Fat shaming needs to make a comeback because some amount of shame is good.” And, you know, there are a lot of people like me who — I’m healthy, I can bike a hundred miles, I can go climb tall mountains, but, like, medically, I am classified as overweight. Now, obviously, sometimes medically things don’t work super well because, you know, by some of the classifications, Tom Brady was considered overweight ’cause of his height and size, but he was muscular and whatever. So these scales are all not scientific and not perfect in any way. But generally speaking — we always use this phrase, “fuzzy math over time still shows trends.” I think generally speaking, the metrics work, but they’re not great in any measure.

DUCKWORTH: So, like, you’re saying that you’re not just Tom Brady who is such high percentage muscle.

MAUGHAN: Shockingly, a lot of people walking down the street do think like, “Whoa, is that Tom Brady?” Just kidding.

DUCKWORTH: Yeah, you can easily get mistaken for Tom Brady.

MAUGHAN: No one has ever thought that.

DUCKWORTH: But B.M.I. is just easy to calculate, right? Like that’s just, you know, a height and weight that you can take and —.

MAUGHAN: B.M.I. is a garbage metric by almost all standards. So, Bill Maher on his show says, and I quote, “Fat shaming needs to make a comeback and that some amount of shame is good.” So James Corden, who’s a British comedian — he’s done The Late Late Show in the U.S. for years at this point, he has since retired — is watching this. And James Corden is himself overweight. And he said he sat watching this and thought, “Man, I wish someone with a platform who’s overweight could say something about that.” And then he is like, “Wait, that’s me.” And this is what he said in, in sort of his response, his monologue response to Bill Maher. He just said: “Fat shaming never went anywhere. Ask literally any fat person. We’re reminded all the time on airplanes, on Instagram, when someone leaves a pie on a window sill to cool and they give us a look like, ‘don’t you dare’” — obviously he’s joking with this last part. But like, he says there’s this common and insulting misconception that fat people are stupid or lazy. And Corden says, “We’re not. We get it. We know being overweight isn’t good for us.” He said, “I’ve struggled my entire life trying to manage my weight. If making fun of fat people made them lose weight, there would be no fat kids in school, and I’d have a six pack right now.” And he ends by saying this to Bill Maher. He says, “When you’re encouraging people to think about what goes into their mouths, please just think a little harder about what comes out of yours.”

DUCKWORTH: Oh, that’s a really good phrase. I think, perhaps, dragging you through the mud of understanding what nature and nurture really are in making us who we are — I mean, look, I don’t know if it’s as good as what you just said, but I hope it prevents us from shaming anyone for anything. You don’t know about the uncountable number of environmental experiences they’ve had. You sure as hell don’t know their full genotype and what those implications are. So, maybe — and this may be naive — but maybe at least appreciating that we’re all really complicated, and it’s just not a simple thing about, you know, you were or weren’t motivated; you do or don’t care about your weight; you do or don’t have fat genes. Like, it’s super complicated. And what I do know is that I have to order lunch today, so what intentional decisions can I make? So, you know, nothing about Ozempic, to me, made me think differently about nature nurture. That had no bearing on this, like, foundational, complicated question. It is settled. Nature versus nurture is the wrong question. How much nature, how much nurture is also an oversimplified question. The answer is nature and nurture in a very, very complicated, non-linear, interactive way. And, whatever your genes are, you always have something that you can do. And at the same time, whatever you do, you’re always going to have your genes.

MAUGHAN: You know, I think the thing that’s been most motivating to me in terms of losing weight — I had a really good friend, Michael Katz, who just came to me years ago and he said, “I care about you and I want you to be around for a long time, so I want you to take better care of yourself.” And that to me was a really powerful external motivator — that he wasn’t shaming me. He was saying, “I care about you a lot. I want you to be here.”

DUCKWORTH: It’s like the opposite of shame, in a way.

MAUGHAN: Right, because it was this caring approach to it, I took it as: he wants to help me. He wants me to be better. He wants me to be around to be a uncle to his kids and everything else. And that had a really powerful effect on my desire to not only believe that I could do something about it, but that I was going to get up and do that.

DUCKWORTH: I mean, this may be a bridge too far, but I’m going walk over it and see if it holds up, which is that, I think really understanding the complexity of how we become who we are, really having some grasp on the fact that like, wow, we’ve just got, like, a gajillion genes and got a gajillion experiences, and they all interact with each other — I do think it brings you to a more enlightened place where you can say to yourself and someone else, like, “There’s so much I don’t know about you. There’s so much I’ll never know about your DNA. And I do know that I care about you. I want you to be here. And maybe I also know that you have some control over what you do, and I have some control over what I say.”

This episode was produced by me, Rebecca Lee Douglas. And now here’s a fact-check of today’s conversation: Angela says that mapping out the eye colors of her family tree was, quote, “easy, cheesy, lemon-squeezy” because all of the members of her Chinese family have brown eyes. She likely meant to say “easy, peasy, lemon-squeezy,” a phrase which reportedly came from a 1950s British commercial for the lemon-scented soap Sqezy. That’s it for the fact-check.

Before we end today’s show, let’s hear some thoughts about last week’s episode on self-compassion.

Logan THOMPSON-DE SA: Hi, my name’s Logan. I don’t have a great answer for the question of how I show myself compassion in chaotic times. I’m still working on that. But I do think there’s a lot of benefit to having a conversation with your friends about the kind of things you say to yourself. I decided to ask one of my friends slash co-workers if she feels she’s very self critical. You know, we had a really nice conversation about it and towards the end I mentioned to her, like, I have the tendency to come home from work and think about something dumb that I said or a mistake that I made and say to myself like, “Oh, you f***ing moron.” And she looked at me and said, “I would punch somebody who said that to you.” Honestly, it made me tear up in the moment. But, since then I, uh — anytime I think to myself, “Oh, you f***ing moron,” I stop myself halfway through and I think about that conversation.

That was listener Logan Thomson-de Sa. Thanks to him and to everyone who shared their experiences with us. And remember, we’d love to hear your thoughts on the nature/nurture debate — especially how it relates to characteristics like weight. Send a voice memo to NSQ@Freakonomics.com, and you might hear your voice on the show!

Coming up next week on No Stupid Questions: Do you have imposter syndrome?

DUCKWORTH: God, I am overrated. People are gonna find me out. 

That’s next week on No Stupid Questions.

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No Stupid Questions is part of the Freakonomics Radio Network, which also includes Freakonomics Radio, People I (Mostly) Admire, and The Economics of Everyday Things. All our shows are produced by Stitcher and Renbud Radio. Lyric Bowditch is our production associate. This episode was mixed by Eleanor Osborne. We had research assistance from Daniel Moritz-Rabson. Our theme song was composed by Luis Guerra. You can follow us on Twitter @NSQ_Show and on Facebook @NSQShow. If you have a question for a future episode, please email it to NSQ@Freakonomics.com. To learn more, or to read episode transcripts, visit Freakonomics.com/NSQ. Thanks for listening!

DUCKWORTH: So, when, you know, like the hand goes up in an audience that I’m speaking to and they ask me, “Is grit nature or nurture?” And I have 10 seconds to answer the question. I’m like, “Heh, well —”

MAUGHAN: It takes all the grit you have not to hit that person.