Weight loss is as simple as “calories in, calories out,” right? Or — gasp — could the reply guys be wrong!? This week, we dig in on the surprisingly complex science behind a seemingly simple calculation.
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Michael: Wait, I need one.
Aubrey: You need one.
Michael: I had one, but then my tagline was a spoiler. So, I'm going to say something else.
Aubrey: Wait, what is it a spoiler of?
Michael: Okay, I was going to say, welcome to Maintenance Phase, the podcast that raises a cubic centimeter of water by one degree.
Aubrey: Oh, buddy. That's the first five minutes. [laughs]
Michael: Welcome to Maintenance Phase, the podcast that recommends 2,000 of it per day.
Aubrey: No, that's a-- [laughs]
Michael: That was so worst.
Aubrey: [laughs] No, I love it. Leave it.
Michael: That's best by far my worst one. I'm sorry.
Aubrey: We have not done a "Me" episode in a while and it's showing up how rusty you are.
Michael: [laughs] I've never cohosted the show before.
Aubrey: I'm Aubrey Gordon.
Michael: I'm Michael Hobbes.
Aubrey: And today, as you may have gathered, I don't know how you would have gathered this. We're talking about calories.
Michael: We're doing calories.
Aubrey: Before we get to that if you'd like to support the show, you can do that on Patreon or you can buy t-shirts, mugs, tote bags, all manner of things at TeePublic. Both of those are linked for you in the show notes. And today, Michael Hobbes, it is the first of a two parter.
Michael: A calorie diptych.
Aubrey: We have gotten a bunch of emails from listeners, particularly, the listeners in the UK wanting us to talk about this new mandate in the UK to add calorie labeling to restaurant menus. And as I got into that research, I found that there was a ton of stuff that I did not know about calories and just straight up how they work. Today, we're going to talk about, we're going to do part one of our two parter. I am calling this one "The trouble with calories."
Michael: Oh, okay.
Aubrey: And next time, we're going to do a deep dive into the history of this food and menu labeling. We'll give a little teaser taster of it today.
Aubrey: It really blew my mind. I think I and many others have thought of calories as being like a very straightforward measure with very clear science behind it. And as per usual, everything is muddier than we think it is.
Michael: Did you think that it was simple because men on the internet are always shouting calories in, calories out at you?
Aubrey: Oh, you busted me again.
Michael: I know. Doesn’t she know?
Aubrey: You already did it. But Mike, can you tell me what a calorie is?
Michael: Okay. I'm going to fuck up the specifics, but isn't it the amount of energy that it takes to raise a cubic something of water by one degree? It's like you burn, I don't know, a piece of paper underneath a little cube of water, and the water gets slightly warmer, and you're like, "That's a calorie."
Michael: Is that right?
Aubrey: You suspend water in a cubic shape in the air over an open flame. [laughs]
Michael: Over a Zippo lighter. Yes.
Aubrey: Yeah, that's right. Yeah. So, that's it. Cubic something is exactly right. You're leaving a blank for that space, because we talk about calories. There are two versions that people talk about.
Michael: Oh, the dumb kilocalorie thing, or kilojoules, or whatever.
Aubrey: We're going to get emails if I don't say it. So, I'm going to say it. [laughs]
Michael: Sometimes, you look on labels. Especially, if you're in a foreign country, you look on the label and it's like 16,000 calories. You're like, "I don't understand." But then you're like, "Oh, they're using the weird calories."
Aubrey: Yeah, the little calories.
Aubrey: In physics, historically, the small calorie is defined as the amount of energy that is needed to increase the temperature of one gram of water by one degree Celsius.
Aubrey: Most of us when we talk about a calorie are talking about a kilocalorie. That's the amount of energy that it takes to raise the temperature of one liter of water by one degree Celsius and that's at sea level.
Michael: Oh, right. Of course.
Aubrey: Because boiling points are different at different elevations, blah, blah, blah.
Michael: I learned that from the back of the macaroni and cheese box.
Michael: But then it's one of those things where it's like, I know what a calorie is in the scientific description. I can put all of the words into that order, but that doesn't actually answer the question, because the way that we interact with calories is like a Snickers has, I don't know, 250 calories. And so, it's like, "Okay, well, are they putting a Snicker under the water cube, and lighting the Snickers on fire, and seeing how hot the water gets?" To me, that scientific definition doesn't actually get at what a calorie is really.
Aubrey: I really appreciate that you're just here to pave the way for what comes next that you're like, "I have a question about this" and I'm literally the next bullet point in my show notes.
Michael: I'm like, "But Aubrey, what does that mean?"
Aubrey: But how do you determine it?
Michael: I know.
Aubrey: [laughs] There are many different ways to measure calories, many different kinds of what are called calorimeters. The most widely known and widely used one is called a bomb calorimeter. It is a sealed container that is filled with pure oxygen and it is suspended in a container of water. Inside that sealed container filled with pure oxygen, you put your Snickers bar, say, to determine how many calories are in it. You ignite it using electrical fuses in this case in that pure oxygen chamber, and it gives off heat into this bath of water that it's suspended in, and you've got a thermometer in that bath of water.
Michael: So, I was right about them lighting Snickers on fire.
Michael: I was joking.
Aubrey: Nope, that's what they do.
Aubrey: It is worth knowing that the history of how calories first appeared in written texts and in scientific literature is actually pretty disputed. I looked into a bunch of different historical sources on this. And basically, the closest that folks get to agreement is that calorie was coined as a term to measure heat in scientific literature sometime between 1787 and 1824.
Michael: Oh, wow. So, lots of gaps.
Aubrey: Big gaps. Some people are like, "It came out of France," and some people are like, "It came out of Germany," and some people are like, "It came out--" You know what I mean? It's disputed where it first showed up, who came up with it, what they were referring to.
Michael: Right. It's like Nutella or fascism.
Michael: It's like, "We know it's from Europe," but it's not clear where.
Michael: Behind that region.
Aubrey: So, in that early era in the 1800s-ish, when calories are coming into more common use in science, calories were established as part of the original metric system.
Aubrey: And it starts being used in commerce in the UK and the US starting in the mid-1800s. But we don't really start talking about food calories and kilocalories more broadly until the late 19th century. The first use that I was able to find is that it was first published in a US medical textbook in 1894.
Michael: This is a constant theme on this show of how young a lot of nutrition science is.
Aubrey: Yeah, it's really, really young, and also really, really old, because some of this stuff hasn't really been revisited.
Michael: Oh, nice.
Aubrey: So, what I wanted to do today is just dig into a few of those core assumptions that we were talking about earlier. I wanted to start by digging in on calories in, calories out, which is almost like a dieting meme at this point.
Michael: Yeah. My God.
Aubrey: Mike, tell me about your thoughts and feelings about calories in, calories out. I'm sure you've heard it until you're blue in the face.
Michael: You know I have a spiel about calories in, calories out. [laughs]
Aubrey: Tell me.
Michael: I have a thing that I say whenever I'm confronted with this, because as you also know, probably much better than I do. The minute you start talking about fatphobia in society or anything involving this issue at all, you will hear the phrase, calories in, calories out within 45 seconds. And then when you push back and you're like, "Ah, that seems a little bit simplistic." What you'll often hear is like, "Well, it's true. Are you saying it's not true? Oh, we've got a science denier over here." My retort to this is always that human beings do not judge statements only on their truth value. If you say to me, "Mike, my mom was diagnosed with cancer today" and I'm like, "Oh, interesting. Did you know that Titanic sank in 1912?"
Aubrey: Yeah. [chuckles]
Michael: You are like, "Ah, that's a little insensitive, Mike." I'm like, "Actually, oh, you're saying it didn't sink in 1912? When did it sink, Aubrey?"
Aubrey: We got a science denier on our hands here.
Michael: To me, the phrase, calories in, calories out has always had the same amount of usefulness as saying like, "Well, to win a basketball game, you have to score more points."
Aubrey: Yeah. [laughs]
Michael: And then the coach is like, "Well, one of my kids broke his ankle and the bus isn't here to take us to the arena, where we have to play" and it's like, "Ah, ah, ah, to win a basketball game, you just--"
Michael: and Aubrey: "You have to score more points."
Michael: Right. It's true that's how you win a basketball game, but that doesn't tell you how to win a basketball game. I'm not coming to you with a question like, "How do I win a basketball game?" It's like, I'm coming to you with a very specific concern and you are then going back to the highest imaginable level of abstraction and telling me the number one first fact about a basketball game that obviously if I'm a basketball coach, I already know. When people say, calories in, calories out, it's not useful.
Michael: And so, whether or not it's true is completely irrelevant. It's not an appropriate thing to say in 99.9% of situations in which it is said. That's my spiel.
Aubrey: I feel you. It's a thing that people say overwhelmingly in bad faith.
Michael: Yes, good God.
Aubrey: Overwhelmingly, it's not coming from people who are seeking to understand. Because if they were seeking to understand, it would be a question instead of a weird challenge, or a statement, whatever, right? I have had my own responses to that. They've all been super ineffective, not because there's a perfect thing to say in those moments.
Aubrey: But because when someone tells you like, "It's just calories in, calories out." They're telling you they are not gettable and don’t want to understand. We're going to talk about the science of this stuff because I find it really interesting, and it's been really illuminating, and fascinating, and has given me a whole lot more to work with. But this episode is not going to give you rejoinders to people who say that.
Michael: This isn't the clapback episode. [laughs]
Aubrey: This is not the clapback episode.
Michael: Only clap backs.
Aubrey: More is it the persuasion episode, right?
Aubrey: My ineffective response to the calories in, calories out stuff, I've run through a few of them, but one of the earliest ones was people would be like, "It's calories in, calories out." And often, they'll say, "It's the first law of thermodynamics."
Michael: Yes. Oh, I love that one, the physics.
Michael: Whenever they bring up physics [crosstalk].
Aubrey: The law of conservation, the idea that energy can't be created or destroyed in a closed system.
Michael: Yeah. Thanks, Bill Nye. Really smart. Thank you for that. I appreciate your comment.
Aubrey: Cool. Good bowtie.
Aubrey: The response that I came up with early on to this stuff, which I don't recommend was I would be like, "Oh, yeah, well, the first law of thermodynamics only applies to closed system."
Michael: [laughs] You tried to out Bill Nye then. That's good,
Aubrey: I tried. It's link. So ineffective.
Michael: [laughs] The reason why that's ineffective, Aubrey is because you're assuming that they know or give a shit about thermodynamics.
Michael: People who bring up thermodynamics right after calories in, calories out don't know shit about thermodynamics, I guarantee. [laughs]
Aubrey: I'm sure you're right. Because if you do, you know what a closed system is, right? Which is nothing gets in, nothing comes out. Our bodies are not closed systems. You're constantly eating food, breathing air, you're in an environment.
Aubrey: And there are quite a few research papers that I read in the lead up to this that were like, "Can we stop with thermodynamics and human bodies."
Michael: Yeah. [laughs]
Aubrey: A bunch of researchers were like, "This is not what it's about everybody."
Michael: I love thinking of you doing only if it's a closed system and then lifting up a microphone and dropping it on the ground be like, "Yeah."
Michael: "Got you."
Aubrey: So, I decided to look into where did we get this idea of calories in, calories out? Where does it first appear?
Michael: Yeah. What fucking message board that this first show up on? Jesus Christ.
Aubrey: The message board of the American Journal of Clinical Nutrition in the year of 1959.
Michael: Wait, really?
Aubrey: Uh-huh. There is this paper that gets published in this Nutrition Journal, by an MD named Max Wishnofsky. "Calories in, calories out is sometimes referred to as Wishnofsky's rule." He laid out an analysis of existing literature on weight loss, and calories, and food, and all that kind of stuff. And concluded that each pound of fat lost or gained, each pound of fat tissue contained 3,500 calories.
Michael: Oh, that's the origin of this thing, too?
Michael: Ah, this comes up a lot.
Aubrey: We're going to get so many little Rosetta Stone moments of like, "Wait a minute, that thing that comes from this?"
Michael: This is the basis of like, if you switch from, I don't know, a supersize meal to a non-supersize meal over the course of a year, that'll save you 17,000 calories, and then you'll lose six pounds in a year or whatever. This 3,500 number is always invoked in these conversations.
Aubrey: Yeah. Switch from whole milk to skimmed milk. Before you know it, you will have dropped three pounds without even thinking about it or whatever. Yes. He determines that each pound of human fat tissue, human adipose tissue has the what he calls the caloric equivalent of 3,500 calories. From there, he concludes that cutting 3,500 calories from your diet would lead to the loss of one pound of fat tissue. Years later, there's this very influential medical textbook. It's called Modern Nutrition in Health and Disease. It takes up this Wishnofsky's rule and writes that "Losing one pound would require an energy deficit of 3,500 calories." That's where we start to get it seeping out into medical usage world is like, "Okay, we're training up future healthcare providers using this rhetoric." It sounds really solid. It makes a lot of sense on its face.
Michael: Right. You can see how it becomes individual diet advice, because then it can easily be-- Well, if you cut 500 calories a day, then you'll lose a pound a week.
Aubrey: Right. It seems here's the answer. We figured it out everybody. 1959, we did it. You can totally see for all of those reasons. You could see why this takes off, right?
Aubrey: And also, this is an idea from the 1950s.
Michael: Yeah. [laughs]
Aubrey: We have had really substantial advancements in the last 60 plus years and we're still in a tough spot with figuring out a bunch of this stuff. In those 60 years, though, a bunch of the assumptions that Max Wishnofsky made in developing this calories in, calories out approach have since been disproven.
Michael: I know where you're going with this. So, I'm remaining silent.
Aubrey: Go. No, tell me where you think I'm going with it.
Michael: My understanding of the current science is that the human body isn't just a little calorie processing machine that your metabolism slows down and speeds up according to all kinds of internal systems. If you eat 3,500 calories, fewer, you don't just keep losing a pound a week until nothingness, until like the singularity. Your body eventually is going to adjust and you're going to plateau.
Aubrey: Totally, totally. And even highly active people, if you apply this kind of formula of calories in, calories out to Michael Phelps, who eats 7,000 calories a day, you'd be like, "That guy is getting fat," even with the levels of activity that he has. But he's not. There are people that we all know who eat very small amounts and are fat people or eat very large amounts and are thin people. He assumes that weight loss is a totally linear process and it's almost like a ledger. Like you make a deposit or you make a withdrawal and that's it.
But he's using a bomb calorimeter to determine all of this and human beings are not containers of pure oxygen suspended in water. When you take in less energy, your body also expends less energy. Over time, it does get harder and harder to lose weight. You lose less and less weight over time if you're restricting calories. And not only that, but when you lose weight, you're losing fat. Yes, but you're also losing muscle mass.
Michael: Right, which burns calories.
Aubrey: Which burns calories. So, that also really complicates things.
Michael: Right. Wait, do you want to hear one of my calories in, calories out zingers?
Aubrey: Ooh, yes, please. You're like, "I know you said it wasn't the clapback episode, but--" [laughs]
Michael: But I've a clapback. I've never actually used this. The thing is, I always, because people always saying like, "Uh-uh, calories in, calories out is true." I'm like, "Well, it's an accurate theory, but there's just two problems." The first problem is calories in and the second problem is calories out.
Aubrey: Yeah. [laughs]
Michael: It turns out both of those things are actually significantly more complicated.
Aubrey: Yes. By today's standards, the evidence that Max Wishnofsky was using to create this Wishnofsky's rule, this calories in, calories out thing would be considered weak. It would be considered weak evidence by today's standards, right?
Michael: Ooh, you're getting Cochrane on them.
Aubrey: Since then, researchers have found a ton of things that influence our ability to lose or gain weight from hormonal influences, to genetic markers, to environmental changes. There are lots and lots of things and none of that is captured in this very simple equation.
Aubrey: The exact thing that makes it so tempting to believe is the reason that it's not very accurate or useful.
Michael: Very simple. It's just like a simple number.
Aubrey: Yeah. Earlier you mentioned your body does downshift. It gets harder to lose weight as time goes on. In 2011, this researcher named Kevin Hall does some research to directly challenge Wishnofsky's rule. What he found was that if you only factor in that metabolic downshift and burning fewer calories, Kevin Hall found that Wishnofsky's rule overpredicted weight loss by 100%.
Michael: Oh, wow. So, basically, people are cutting 3,500 calories from their diet and they're losing half a pound, not a pound.
Aubrey: Over time. Part of the way that this works is it's a declining graph. The longer you restrict your calories and the more you restrict your calories, the more your metabolism downshifts, the fewer calories you burn, and the harder weight loss gets, right?
Aubrey: He did this over the course of a year. He said that, "Calories in, calories out would say you would lose twice as much weight as you actually would, given the way that your metabolism downshifts." I'll also say there is some research, most famously with the Biggest Loser study that finds that calorie restriction in the long-term actually damages your metabolism and that downshift is permanent. In 2015, just four years later, there's a paper that is released in the Journal of the Academy of Nutrition and Dietetics and they tried to do this omnibus like, "Here's everything that's wrong with calories in, calories out." It's authors essentially concluded that the rule is easy to use, Wishnofsky's rule and calories in, calories out is easy to use, but "lacks a contemporary scientific foundation and leads to a large error in weight loss prediction even over the short term."
Michael: That's the mic drop. That's the actual one.
Aubrey: That's the mic drop.
Aubrey: It doesn't account for anything we've learned in the last 64 years. There are a few things that they point out. One, they point out that it doesn't account for the energy that's actually expended in digesting your food. We now think that between 10% and 15% of the calories of given food are actually just used in the digestion of that food.
Aubrey: Take 10% off the top, it also doesn't account for a ton of stuff that we've learned about your endocrine system, and hormones, and how those influence body shape and size. It doesn't account for cortisol, or ghrelin, or insulin. All of those are hormones that are known to impact your digestion, your blood sugar, your hunger and satiety cues, all of that kind of stuff is completely left out of this. It also doesn't distinguish between what the difference is between calories from different sources. It's not distinguishing between calories from fat versus carbs versus protein, sure, but also, I didn't think the jury was still out on calories from alcohol.
Michael: What? Meaning like they don't count for making you fat or something? What does that mean?
Aubrey: I am going to send you a quote from a doctor.
Michael: Okay. It says, "There's a big debate on whether alcohol calories are even usable, whether you can even turn them into fat. It's not easy," says Ken Fujioka, MD, a weight loss expert at Scripps Health in San Diego. "When you look at various studies you actually get mixed results. Some studies say it's not a problem. Don't worry about it. Others say it's associated with weight gain. So, it's a real open mess." Wait, so--
Aubrey: Yeah, dude.
Michael: It might be the case that just like booze calories don't count.
Aubrey: Ed McMahon might be right.
Michael: I know.
Michael: I'm writing our inevitable diet book in my head right now, actually. [laughs]
Aubrey: I include that not to be like, "Everybody go get wasted." But to be like, "Look, that is a thing that I really thought was a bedrock thing." No, is a really open question about how your body processes calories from alcohol.
Michael: This is kind of the calories in problem.
Michael: Because two people might eat the same meal and both have a hamburger and a beer. And one person will be able to use 800 calories and the other person will be able to use 1,000 calories.
Aubrey: Right. Totally. That's actually another point that these authors of this paper bring up is they're like, "Look, look, look, look, look, even if we came up with the best possible population level modeling of what will generally contribute to weight loss or weight gain at the population level, that's not going to translate into individual behaviors because it can't capture individual biological differences." You can restrict calories all day long for someone with lipidemia. They're not going to lose weight in the same way that a person without lipidemia would lose weight and there's just not really a handy-dandy calorie calculator that incorporates all of those things and can just go, "All right, your personal calorie level is this." No, we don't know how to do that. And even if we did, again, calorie restriction doesn't produce weight loss long term, it slows you way down over time.
The thing that these authors conclude with in this paper is genuinely that models these. these kinds of universal models of like everybody needs to eat this many calories or restrict this many calories and that will lead to this kind of weight loss cannot be used to predict any individual's weight loss or gain. That is how far they go. It's not just like, "There are some exceptions where this wouldn't apply." It's like, "This doesn't work for any individual who could stop using it." And I think that's also borne out by our personal experiences. If anybody's tried to lose weight, you know that you plateau real hard. The longer you go, the harder it gets. That's not you losing your willpower or whatever else have learned to attribute that to. That is your body kicking in and a bunch of bodily systems kicking in to downshift how much energy you burn, and to conserve energy, and to make sure that you have enough energy to continue to live and survive.
Michael: Right. And none of it's in your control at all. It's just an automatic thing that your body does, basically.
Aubrey: Yeah, totally. When this 2015 paper comes out, the debate around calories in, calories out is just continuing to go. There are a bunch of different perspectives on calories, and weight loss, and what really works, and what really doesn't in the research, but they pretty much all agree on one thing. This straightforward just restrict calories thing, calories in, calories out, just doesn't work. The most recent entry into this set of like, "Maybe it's this, maybe it's this, maybe it's actually this," about weight loss and calories is a 2022 paper from the American Journal of Clinical Nutrition that actually argued that the brain is the primary organ that governs weight loss. Not consciously, but nearly all subconsciously. We're trying to consciously act our way out of a thing that is happening in our bodies without our awareness. We're trying to be like, "No, you just need to have enough willpower." Well, a lot of the research shows that willpower around food is just how much ghrelin is in your system. In that same article, they say, "BMI is highly heritable and genetic differences explain approximately 75% of BMI variability among individuals."
Michael: [laughs] Whoa.
Aubrey: Other papers that I read put it at 80%.
Michael: My understanding of people who have lost weight and kept it off for a long time, because like those people do exist is that basically, it's ongoing calorie restriction and they're also exercising a lot more. Their body never gets to the lower setpoint. The amounts of weight that people are able to keep off over the long term are relatively small. It's like people that have lost 10% to 20% of their body weight. The data on this is really bad because the only source of data on this is this thing called the National Weight Loss Registry, which is self-reported and no one knows how true any of it is.
Aubrey: Yeah, I will say in all of the research that you and I have done for the show, maybe you have seen something I have not. I have yet to see data that shows someone who was fat for their whole life becoming thin and staying thin.
Michael: That's interesting. Yes.
Aubrey: I have definitely heard about people who are like, "Oh, I gained 20 pounds or 30 pounds through my pregnancy. And now, I need to lose it."
Aubrey: I have heard stories, and anecdotes, and seen data about thin people restoring their thinness. I have not seen or heard stories of fat people becoming thin and staying that way.
Michael: That's a really good point. I've heard this from doctors that when somebody comes in who has lost more than 10% of their weight, the doctors will be like, "Oh, you were only at that higher weight for like three months."
Michael: It's usually these brief periods. But yeah, that's a really interesting distinction. I also have not heard of someone who's just been fat their whole life, taking it off and keeping it off. Although, I'm sure those people exist, because it's a big country and something about it exists.
Aubrey: Yeah. I'm not going to say it doesn't exist. I'm just going to say like, "it doesn't show up very often in the research because so much of the research is geared toward how do we find effective methods of weight loss--"
Michael: and Aubrey: Which is all temporary.
Aubrey: And all of which is built around the expectations of thin people and thin bodies, right?
Aubrey: I don't offer any of this up to drive us toward better weight loss solutions or any of that kind of stuff.
Michael: Good God.
Aubrey: But just to illustrate how deeply wrongheaded our assumptions about weight and weight loss are and fatness and fat people are. It's incredibly clear in this research that calories in, calories out is not a thing. It shows up everywhere, and we've just accepted it pretty uncritically, and researchers are not accepting it uncritically.
Michael: It's also very interesting that these findings bounce around technical fields or more STEM-y fields were just like, "Oh, yeah, it's really difficult for anybody to lose weight and a lot of it's inherited." And then when you look at the sociological conversation, the popular conversation and the political conversation, it's like none of that stuff has jumped over.
Michael: The conversation about it is like, "Well, we're doing a municipal project to help everybody lose weight."
Michael: It doesn't engage with this literature at all.
Aubrey: Not only does it not engage with the literature, it engages with literature that has been actively disproven and debunked, right?
Michael: Right. [laughs]
Aubrey: It's actively like, "Now, let's pull out the bad stuff that doesn't work" and that makes people feel bad, and that everyone hates, and that we've tried a bajillion times like da, da, da, da. Let's do that. Okay, so, I'm going to move us on to the next thing. That was assumption number one. We got moves to make here.
Michael: So, tripartite structure.
Aubrey: The next assumption that I wanted to look at is the idea that the calorie counts that we see on food labels, or restaurant menus, or whatever are an accurate and useful set of information in understanding how our bodies use those calories.
Michael: I am so interested in this.
Aubrey: I am so excited to tell you about it.
Michael: There's no way those Chipotle calorie things are accurate. There's no fucking way. [laughs]
Aubrey: [laughs] Okay. All of this calories in, calories out shit assumes that human bodies operate in the same way as a calorimeter. We don't. Digestion takes time. It's a bunch of chemical reactions are happening in your body. It's real slow and our bodies don't actually extract all of the calories in a given food. You might be eating 200 calories worth of something, but your body might only be able to absorb 100 calories of it.
Aubrey: Before we start this section, I want to give a content note specifically for Michael Hobbes.
Michael: Oh, no.
Aubrey: This section is going to include poop stuff. So, I apologize in advance for poop stuff.
Michael: I could see it coming. [laughs]
Aubrey: You could see it coming? Uh-huh?
Michael: I've been tensed up since I heard the word digestion, the first time in the episode.
Aubrey: Yeah. Sorry, it is happening.
Michael: The veins on my neck sticking out. Yeah.
Aubrey: Some folks may have heard that we use nine calories in each gram of fat and four calories each per gram of protein and carbohydrates.
Michael: I have absolutely come across this. Yeah.
Aubrey: Those numbers come from a surprising source I think. They were developed about 120 years ago and the person who really put this on the map was a chemist and a chemistry professor named Wilbur Atwater. Is this a name you've ever heard before?
Michael: I don't think so.
Aubrey: He's the son of a Methodist minister, who's also a law librarian, normal combo. He's born in 1844. So, we're talking about the 1800s here. He grew up during the temperance movement. Do you know about the temperance movement?
Michael: It's like a bunch of ladies saying like, "Don't drink."
Aubrey: Yeah, pretty much. His father in this case, the minister/law librarian was a huge advocate of temperance.
Michael: Oh, okay.
Aubrey: I feel that is a way to say this dude was presumably around a lot of rhetoric around "resisting temptation."
Michael: Oh, right.
Aubrey: Atwater was a professor of chemistry at Wesleyan after he graduated from Yale from 1873 until he died in 1907. He was there four decades. He was the USDA's first chief of nutrition investigations. He also in 1896 published the first guidebook to the nutritional values of different foods that we eat. It was called The Chemical Composition of American Food Materials.
Aubrey: What it tried to do was spell out how much fat, carbohydrates, and protein is in each food and how many calories are in each food?
Michael: Right. We've identified calories and he's trying to break foods into their constituent parts. What are the calories mean, basically?
Aubrey: Yeah. It is also worth knowing that the aforementioned Women's Christian Temperance Union ended up running a campaign against Atwater.
Aubrey: Because he ran an experiment on the caloric value of liquor.
Aubrey: He had a test subject in his study. He put this test subject on a diet of mostly alcohol for six days-
Aubrey: -and was like, "Well, this person didn't die. They kept living. Their body kept working. So, alcohol is a food." Women's Christian Temperance Union was like, "Fuck off. Get out of here."
Michael: I love the days of science where it was like, "Let me just hit someone with my car and see what happens."
Michael: Oh, yeah. [laughs]
Michael: That was like a study.
Aubrey: Oh, make this guy drunk for six days.
Michael: Yeah. [laughs]
Aubrey: At this point, French and German scientists had done some work to define calories and learn some basics about how they worked. But it wasn't clear whether fats, and carbs, and proteins were all utilized in the same kind of way. So, that's what he tries to figure out. Can I tell you how he figured that out, Michael?
Michael: Is he just setting a bunch of fat and carbs on fire?
Aubrey: We talked earlier about calorimeters and bomb calorimeters in particular. He's measuring the calories in a given food and then what he wants to find out is, what's the caloric availability of that food? Of those calories, how many can your body use? The way that he does that is he calculates the caloric value of a food and then he feeds that same food to a bunch of different humans.
Michael: No, no.
Michael: I know where this is going now. I know why you warned me.
Aubrey: He collects their poop after they eat that food, and then he burns the poop in the bomb calorimeter.
Aubrey: Caloric value of the food minus caloric value of the poop equal calories you absorbed and used.
Michael: I refuse to understand how poop works.
Michael: But is that accurate? Does that give him a reasonable count?
Aubrey: For more than 50 years, researchers have known that these Atwater factors are not necessarily wrong, although possibly totally wrong, but not the whole picture.
Aubrey: So, I just sent you a quote. This is from an article in the New Scientist.
Michael: Okay. It says, "Well Atwater took into account the fiber in food, which we can't digest." Hello, sweetcorn. "As well as the nitrogen extracted from protein and excreted as urea in our urine, he didn't take into account the heat given off during metabolism. This is known as diet-induced thermogenesis and is the significant energy cost of converting protein, fat, and carbs into the amino acids, fatty acids, and glucose that our body needs." Okay, so, the food to poop pipeline is leaving out a bunch of extra stuff that would have affected the calorie counts.
Aubrey: Totally. And I think this is another place where it's reasonable to assume that because of all the individual differences that we talked about before, this is probably not super useful as an individual guideline. This is a little part of the picture. It's a real old dusty little part of the picture.
Michael: Do we have a better estimate now on fat, carb calories? Have these numbers been adjusted or are we just like, "Eh, we think they're in the ballpark?"
Aubrey: They may be in the ballpark, but again, it's less about whether or not those numbers are right or wrong and more about how they're contextualized within other body systems. The reason to drill down on these numbers would be to get a better sense of how to restrict calories for weight loss. We already know that that's not actually a super functional method across the board. Again, not saying it doesn't work for anybody, but for the most part, when we look at these numbers in the aggregate, it just doesn't work for the vast majority of people.
Michael: Well, we also know from our SnackWell's episode that this thing of fat being way more calorific is one of the reasons why we got decades of low-fat dietary recommendations.
Aubrey: Yeah, totally.
Michael: So, this stuff really matters. Even if it's on pretty shaky, poopy foundations.
Aubrey: [laughs] Yeah. I think all of this stuff matters not because of what it means for like, "How to maintain or lose weight?" But because of how it influences the diet industry, and how that diet industry shapes culture, and shapes our cultural understandings of each other's bodies and our own bodies. That's the stuff that I find most fascinating about all of this is just how far apart those worlds are of science and research versus what is able to be commodified, what is able to be sold, what is able to be used for advertising?
Michael: Right. And is belief that it's like, it must be real, because it's numbers.
Aubrey: Totally. And I would also say, listen, we talked about calories in, calories out gets deployed in this totally fucking bad faith way, right?
Aubrey: But I also think we deploy it in pretty bad faith ways with ourselves, too. The self-talk that folks will use when they are restricting calories, can be really, really cruel and can be really, really unforgiving, and that also becomes how they learn to think about other people who they perceive as failing to lose weight, which includes fat people, right?
Aubrey: Okay. So, the next assumption that I wanted to look at is this idea that we should all be aiming for 2,000 calories a day.
Michael: Ooh, yeah.
Aubrey: I think most of us presume that 2,000 calories per day is the correct amount of calories to eat if you want to maintain the same weight.
Michael: Right. Even though, every fucking label says on it like, "This is not recommended for individual use."
Aubrey: Not low-calorie food.
Michael: Yeah. It's even on there of like, "Don't use this" and then everybody uses it.
Aubrey: Yeah, that's right. Marion Nestle wrote a great piece for The Atlantic called "Why does the FDA recommend 2,000 calories a day?" I learned so many things from this piece.
Aubrey: One, nutrition labels are super fucking new. They've only been around since 1994.
Michael: Oh, wow.
Aubrey: Before 1994, labels on food were super-duper limited. Basically, manufacturers pretty much only had to report nutrition information in their foods if they were making a big nutrition claim or if that food was fortified with vitamins, or minerals, or protein.
Michael: Wait, so, if I picked up a Lucky Charms box in 1992, it wouldn't have any information on it. It wouldn't have the ingredients.
Aubrey: It would because cereal is fortified with vitamins and minerals.
Michael: Oh, interesting. Okay.
Aubrey: That iconic nutrition label of black text on a white background with those horizontal lines in the US has only been around since 1994. They were adjusted a couple of times in 2006. They added a line for trans fats.
Michael: Yeah, I remember that.
Aubrey: In 2016, they updated them again. Those changes didn't show up until 2020. Basically, they changed a bunch of serving sizes. Interestingly, ice cream went up in serving size from a half a cup to two-thirds of a cup.
Michael: Yeah, but those suck in serving sizes.
Aubrey: They also dropped the requirement to label the content of vitamins A and C because as it turns out, Americans generally get a lot of those.
Aubrey: So, instead, they swapped that out for vitamin D, dietary sources of vitamin D, which Americans generally don't get enough of according to the FDA and USDA.
Michael: That seems like a good change.
Aubrey: Right. I was like, "Sure, these all seem reasonable." But the other thing that they did with that most recent label change, which you might have noticed, I definitely did is that calorie counts on packages got huge.
Michael: Oh, yeah, they did the graphic design update. Yeah.
Aubrey: They got really big, and really bold, and they are like, "This is the number that matters." So, here's where we get into a wild territory. The FDA says that they didn't actually intend this 2,000 calories per day to be a nutritional guideline.
Michael: What? Don't you guys make the labels? Can't you just not do it?
Aubrey: They said that they designed it to be a popular education tool.
Michael: Wait, what does that mean?
Aubrey: That means that it was designed to be easy for consumers to understand what was in foods, but not necessarily meant to be like here's the hard and fast information/not be a recommendation for every individual that you need to eat 2,000 calories a day. They're like, "No, no, no, we pick 2,000." In part, because it was a round number that people's brains could hook on to more easily, essentially, they wanted consumers to be able to compare the nutritional value of different foods to one another, and compare apples to apples a little bit. But in order to do that, they had to standardize serving sizes, they had to standardize calorie counts, they had to come up with a standardized system, so that everybody was getting the same information.
Michael: Right. So, you can have a Snickers and a Mars bar, one in each hand and you can say like, "Well, this one is 25% of my fat and this one is 31% or whatever."
Aubrey: What do you want to pick? Exactly.
Aubrey: 2,000 calories a day was not based on nutritional or medical best practices. It was not based on recommendations from scientists, it was not based on research into any optimal diet, or weight management, or any of that stuff. It was based on Americans self-reported calorie intakes through USDA surveys.
Michael: No way. [laughs] This show love self-reported dietary information.
Aubrey: I have a bullet point in my notes that just says, "Mike, tell us what's wrong with self-reported calorie intake?"
Aubrey: But we already did that in this episode twice and in other episodes multiple times. I'm like, "We're good."
Michael: Yeah, I bring this up at parties now. All of the data is just garbage.
Aubrey: It's nonsense. So, in those USDA surveys, what they found was put all together men, women and children self-reported consuming between 1,600 calories a day and 3,000 calories per day.
Michael: Oh, see, I was just going to say, most people underestimate the number of calories they're eating per day, because we all want to seem virtuous and eating less is virtuous. So, the 2,000 is way too low. But if the range of self-reported calories is between 2,000 and 3,000, that means the actual numbers are significantly higher.
Aubrey: They essentially decide to aim for the middle of that range. The FDA initially proposes a recommendation of 2,350 calories per day.
Aubrey: Anytime you issue rules, which are like the things that a state agency can just decide for themselves, they don't have to wait on Congress, or the President, or the state legislature, or anything else. You have to have what's called a public comment period. So, I am going to send you-- This is a little bit of a long quote. this is from the Marion Nestle piece about how did we get from 2,350 calories per day as generally the middle of that range that they were provided to 2,000 calories a day.
Michael: It says, "Despite the observable fact that 2,350 calories per day is below the average requirements for either men or women obtained from doubly labeled water experiments, most of the people who responded to the comments judged the proposed benchmark too high. Nutrition educators worried that it would encourage overconsumption be irrelevant to women who consume fewer calories and permit overstatement of acceptable levels of eat less nutrients such as saturated fats and sodium. Instead, they propose 2,000 calories as consistent with widely used food plans close to the calorie requirements for postmenopausal women, the population group most prone to weight gain a reasonably rounded down value from 2,350 calories easier to use and 2,350 calories and therefore a better tool for nutrition education. Whether a rounding down of nearly 20% is unreasonable or not, the FDA ultimately viewed these arguments as persuasive." Wow.
Michael: So, it's just like it was easier.
Aubrey: It appears from this account that the primary reasons were, this is going to seem irrelevant to women who are already restricting calories. They just won't pay attention at all. If we tell them 2,350, then they're going to eat more than that. We have to tell them less. It also accounted for people eating more than 2,000 calories. They thought that they would say 2,000 and people would eat more than that. It is introduced this what is in retrospect and entirely arbitrary number. It started out with bad data and they were like, "Here's the middle of that bad data" and then they were like, "No, that's too high."
Aubrey: And then walked it back to 2,000 calories. It just seems this very clear example of the ways that our public policy around food and the information we have access to is just always shaped by our social fears and anxieties around fatness and fat people and our disgust or rejection around fatness and fat people, right?
Michael: It is this very familiar two step, where whenever you criticize these things as the 2,000-calorie thing seems fake and arbitrary, you then get the response that's like, "No, no, it's science." And then you're like, "Okay, let's talk about the science." And then the science is fucking trash.
Michael: and Aubrey: It's not science.
Aubrey: Yeah, totally. I feel you would be hard pressed to find a hardcore nutrition researcher, who'd be like, "Those are good numbers. Good job, FDA." [laughs]
Michael: It's also weird how, if the first step can just be admitting like, "Okay, we chose this number, because we wanted to raise awareness of the dangers of obesity. That's why we did it."
Michael: Okay, fine. You did that then, fine. But now, we know more about obesity and we also know more that this isn't necessarily helping people. And so, if this is an ideological/communications number, then we should probably change it, so that it suits that purpose.
Aubrey: And we should be clear with people that we designed this as a communications tool, not as dietary guidance.
Michael: Right. Which is the way that it's being used my God.
Michael: It also makes these diets, these 1,200-calorie-a-day diets which are very common, even more chilling. Because in your brain, when you hear that of like, "Okay, I'm supposed to eat 1,000 calories a day on whatever diet I'm on." In your brain, you compare that to 2,000 calories a day. That's what my brain does. I'm like, "Ooh, that's half of what you're supposed to be having." But if the original number was 2,350 and it's based on self-reported data, which is artificially small. It's like, "A 1,000 calorie a day diet is a third of what people should be eating in a day."
Aubrey: Well, and when we get into how calorie restriction messes with your metabolism and changes how your body functions, it's not just like, "Oh, we got this wrong." There are repercussions. And this feels the most benign information just like, how many calories are in a food? It's just a fact. Here you go.
Aubrey: And as it turns out, none of those things are exempt from being shaped by cultural values, none of those things were designed as guidelines, and none of those things have neutral impacts. Those are all things that do have implications for your attitude toward food, and your body image, and all other kinds of things. How you feed your family? I feel a little vulnerable in this episode, I will say, because this is all stuff I did not know.
Michael: Me neither, me neither.
Aubrey: It feels a little alarming.
Michael: It's also chilling to contemplate just how entrenched 2,000 calories a day is as a concept.
Michael: It isn't something that's like, "The controversial number, 2,000 a day."
Michael: It's so predictable that it would be used this way, too.
Aubrey: Right. Yeah. If you're like, "Oh, we did it, so that consumers can better understand," well, they would better understand in order to make different decisions. The idea that it would just be for purely educational and informational purposes, but that would not influence your behavior is also naive.
Aubrey: That's it for this week.
Aubrey: I wanted to start us off by laying some groundwork of like, "Oh, shit, calories are not as straightforward as we thought they were."
Michael: Yeah. This stuff is really fraught.
Aubrey: Isn't it?
Aubrey: I feel the deeper we go into this stuff the murkier it gets, but it feels a productive murky. Does that make sense?
Michael: Yeah. I feel we're coming to a theory of science and institutions on the show as we zigzag from episode to episode. I'm always really struck at how consistent it is that scientific institutions are like, "We have to twist the science to get this outcome that we want and the outcome is always like well, everybody needs to be thinner." I don't think anyone seems to have contemplated or asked really basic questions of like, "Is this a goal that we want or is this going to have really predictable, unintended consequences?" I really think the variable is like bias. I think being biased against a group just makes you roll your eyes at their concerns.
Michael: In all these things, it just seems like this really obvious blind spot that nobody seems to have contemplated at the time or brought up at the time in a way that feels very anti science.
Aubrey: Yeah. Listen, we talked about this a little bit way back in our episode on anti-fat bias. There are these astronomical levels of anti-fat bias from healthcare providers directed at their fat patients. I would say the same thing about researchers, and public health officials, and bureaucrats, and all of the folks who are taking up the mantle of continuing the "obesity epidemic" and continuing to drive this public health weight loss stuff. We're all products of a culture that is really, deeply judgmental of, dismissive of, and rejecting of fatness and fat people.
The idea that because someone has an advanced degree in a hard science, they would have also overcome all of those biases and done all of that deep emotional work to get right in their head or that they wouldn't be subject to the same cultural ideas as the rest of us is wrongheaded. We're all in the same soup. It just feels really tricky and laden, and I think folks are looking for someone who could just step outside of our cultural context and be like, "This is the truth. Here's an objective truth and we just don't have that because all of us are in it together."
Michael: Right. We're all in the same pond and this podcast is the burning Snickers that is slowly raising its temperature.
Aubrey: No, this podcast is the burning poop from the person who ate the Snickers.