Mary Harris: Hey, Mom.

Mary Harris’ Mom: Hi, Mary.

MH: I called my mom the other day because I wanted to talk to her about this weird moment in my childhood.

MH: Um, so do you remember that weird diet you put us on back when I was eleven?

MHM: Oh, yes I do.

MH: I was a chubby kid back then, before I hit my growth spurt.

MHM: You had an appointment with your pediatrician and he reported that your cholesterol was high.

MH: So, all of us went on the Pritikin Diet. Lots of fruits and vegetables and whole grains, my mom still remembers sending me to middle school with Tupperware containers full of udon noodles and seaweed. In 1988 that was not a cool lunch.

MH: You know what I remember, those Pritikin books, because they had on them, in pretty large all caps font: NO FAT, NO SUGAR, NO SALT, NO EGGS. And I remember thinking, what am I going to eat.

MHM:  [laugh] It was very vegetable based, there was a lot of chopping going on .

MH: Pritikin is the only diet I’ve ever been on, but for my parents it was just one of so many they tried.

MH:  Can you like tick off the many diets you’ve been on?

MHM: Oh, gosh. I wish, I was at home because then I could read the spines of all the diet books that are sitting on a bookshelf because I was looking at them the other day.

MH: You were?

MHM: I really was. I was thinking this is insane. I mean, the latest one to walk in the door. Oh, gosh I wish I could remember the name of it. Well, there is one called “The Makers Diet”, which is a Christian based diet. I picked up that diet book at the resale shop. I mean Atkins, Pritikin, the latest one, is um, well, there’s the Paleo diet. Oh, dad started the Hollywood diet that was back in the 70s that was very fruit oriented. I remember when we took a trip to California and he was only eating fruit and one day all he ate was one watermelon.

MH: I really think that watching my parents go from one crazy diet to another when I was a kid -- it showed me that the science of what’s good for us is always changing. But there has been this one basic bedrock rule of dieting, right? If you burn more than you eat, you’ll lose weight. And the way we measure what we take in, it’s the calorie. But what if the calorie isn’t all that trustworthy either? Cynthia Graber and Nicola Twilley have been looking into that. They are the co-hosts of Gastropod; it’s a podcast about food, history and science.

MH: I just want to know, what made you curious about this in the first place?

Cynthia Graber: So I’ve actually been curious about this for years. Because I’ve seen family members and friends who are struggling with weight.

MH: This is Cynthia.

CG: They’ve tried to cut calories and they did what they thought they were supposed to do, and they just couldn’t get the weight off. So I was thinking, is it really just a calorie, is it really that simple? That calories in, calories out, that’s the balance? So I started following the research over the years.

Nicola Twilley: For me; it’s like, I’m a compulsive label reader.

MH: And that’s Nicky.

NT: So, I’m the person turning around all the boxes at the supermarket. And the calorie is on every label. It’s like this all powerful number that defines food. And I realized: I don’t know what it is.

MH: So we know a calorie is a unit of energy, right? I had to look it up to remind myself of the exact definition. It’s actually the amount of energy it takes to raise the temperature of one gram of water by one degree Celsius. But Nicky is asking: What do we not know about the calorie? Is it the best way to measure what we eat?

Today on Only Human, we team up with Gastropod to answer those questions. Cynthia and Nicky’s investigation starts in a really important place, Beltsville, Maryland, where there’s a lab that’s spends a lot of time studying the calorie. Here’s Nicky Twilley again:

NT: We went down to this anonymous office building in the suburbs between Baltimore and D.C. It’s the U.S. Department of Agriculture’s like big research campus there. And part of the work they do is looking at calories, how many we burn when doing different things, how different foods change what we burn, all kinds of things like that.

MH: I have to say, the intensity of the federal government’s research into the calorie kind of surprised me. Like, here is one thing the USDA lab does: they bring in regular people and feed them a really precise diet and then they put them in a room.

NT: It’s actually a room that they make people live in for a day or two. You are completely shut in there and so that way, they can measure how many calories you are burning and it’s called a calorimeter.

MH: So, you live in it for a couple days?

NT: Yeah, you have to live in it for 24 to 48 hours. There’s florescent lighting and vinyl tiles and white balls; it feels a little like a low security prison.

CB: And we should say; it’s small. It makes a Manhattan apartment look like a palace.

MH: And this guy, Bill Rumpler, actually showed you around. Cynthia, here you are getting a tour of the calorimeter.

CB: This is literally a walk-in cooler.

Bill Rumpler: We bought this from Nor-Lake, a walk-in cooler company, yeah. Unlike a lot of them, they are sealed fairly tight.

MH: So what goes on in this room? Like, what is it measuring?

CB: So, it’s measuring how much energy you are using and how much energy you are expending. They have sensors in the walls. Sensors measure movement and they measure oxygen and carbon dioxide. They can literally tell how many calories we are burning.

MH: The lab is actually not just measuring how many calories the person is burning, but how many calories a person is taking in, which is why another room is dedicated to painstaking food preparation.

David Baer: Dinner tonight is meatloaf, mashed potatoes, corn, a homemade brown bread, a…

MH: So Nicky, you talked to David Baer, and he was actually in the research kitchen, where they make all the food that they feed to folks that are in these boxes.

NT: Right, they prepare all the meals for volunteers in the studies, in a special research kitchen. And they are super, super, super specific about it. You get a different amount of food exactly based on your gender and height and weight. So there’s this whole room full of people, in the kitchen, people in hairnets putting things on scales and then packaging it up. And it’s amazing, we found it hysterical. If it’s brown bread for dinner, you might get literally an extra crust just to make it the number of calories for your height and weight. I saw them put half a waffle in a little baggie for somebody. And I mean, of course at home you would just eat the waffle, but for this it has to be exactly the right amount of calories.

MH: That guy you heard who was listing off the night’s menu, David Baer, he’s a research physiologist. And lately what he’s been studying is how many calories we get from nuts.

NT: So, they studied three different types of nuts. They first looked at pistachios, and then they looked at almonds and most recently they looked at walnuts.

MH: So the question he’s asking is how many calories that are in those nuts can we actually absorb?

NT: In the pistachio study, they found that we can absorb maybe five or six percent fewer calories than what are on the labels. For the almonds, they found that it’s about 30 percent fewer calories than on the label. And in the most recent one, which is about the walnuts was about 21 percent, so that’s a huge difference.

CB: And it’s really interesting, because if you eat, you know 100 calories of almonds, what it says is a 100 calorie pack, you’re actually only taking in 70.

MH: David Baer thinks there is something about the internal structure of nuts that makes it hard for our digestive system to get the calories out.  On the one hand, this is great! When we eat nuts, we are getting fewer calories than we thought, but also, for me, this is strike one against the calorie.

MH: So the label says one thing, but the truth is something totally different.

NT: Exactly, which is really hard for people who are trying to count calories. I mean, if you’re saying “I just had 100 calories of almonds, so I’m going to change something else and you only had 70, how does that effect what you are trying to put together for your day’s caloric intake?

CB: And it goes the other way too, actually. So, while we were studying this we ended up talking to an anthropologist at Harvard, called Richard Wrangham, and he has study ways in which cooking changes the structure of food, the internal structure of food, but in ways that make more calories available.

MH: And he has kind of a crazy story of how he got interested in calories.

Richard Wrangham: I was studying the feeding behavior of wild chimpanzees. And I tried to eat everything that chimpanzees ate. And I even tried to go for days at a time, eating only what they ate and I discovered that it left me incredibly hungry. It lead me to the thinking that there is something very different about living as a wild animal eating raw foods and living as a human and then I realized that every human eats their food cooked.

MH: So what does this mean?

CB: Well, cooking it turns out, changes the structure of food. But no one had looked into if changing the structure of food, changed how many calories we could get out of it. And Richard did.

NT: So they looked at starches, meat and fats and they found as Nicky was saying that cooking frees up significantly more calories than if you ate it raw. So for starch; it’s about 40 percent more if you eat cooked sweet potatoes than raw. In terms of meat, you get about 20 to 30 percent more calories if you eat a well done hamburger than if you eat a raw steak tartar. And we are not sure with fat exactly what the numbers are, but it looks like from their earlier studies it’s kind of similar numbers.

CB: And the thing that’s interesting about this, I thought is you know this is normal cooking. This just like, what you might do at home. But food processing is like cooking on drugs; it’s high heat, high pressure. You know what it takes to make a Dorito and this extrusion and you know centrifuge and all of that. What’s that doing to our food? Is that making even more calories available? Nobody knows.

NT: And Richard thinks that it might be and that’s what’s really fascinating, right?

MH: So he thinks that processed food actually might be more calorie dense than we even realize.

NT: That’s right. Just because the calories are more available to our bodies.

MH: So let’s recap. USDA scientists have found for some foods like nuts, we absorb a lot fewer calories than packaging would lead us to believe. Like I said, that’s strike one against the calorie. But Richard Wrangham, this anthropologist at Harvard has been doing research showing that by cooking foods, and also maybe by processing them, we get more calories and that’s strike two. And Cynthia Graber and Nicola Twilley say there’s another thing we should know about that calorie: all of us process food differently and some people get more calories from food than other people do.

CB: Yeah, it’s true you know I think people think a lot that this is a genetic difference. There are slight genetic differences among people, but it doesn’t seem like that’s the overall biggest impact. So you probably heard that each of us has a different group of microbes living in our gut. It’s as individual as a fingerprint. 

MH: So you guys also talked to this guy, Peter Turnbaugh, a professor of microbiology and immunology at the University of California San Francisco. And he’s looking into how all of the microbes in our guts actually might change how we absorb calories.

Peter Turbaugh: That concept of a calorie needs to not just take into account the absolute amount of energy that’s possible to gain from a food, but also the variation between us. In terms of how good our own body and our microbes are at liberating those calories.

MH: Okay, so I might be liberating more calories than you guys?

NT: Yeah, you know remember the micorbes in our guts are as individual and unique as a fingerprint. Yours might be more efficient at getting calories out of food than mine. Peter and other scientist have done studies with specially breed mice that have no microbes in their guts. And they’ve taken microbe samples from the guts of human twins, one obese twin [and] one lean twin. Put them in the mice and then the mouse that has gut microbes from the obese twin that mouse ending up gaining more weight, even when eating the same amount of food, exact same diet.

MH: Whoa.

CB: There’s a couple other studies that we thought were absolutely fascinating. And one was on risperidone it’s the active ingredient in Risperdal, the antipsychotic medicine that people day makes them gain a lot of weight.  So the researchers were able to show that risperidone changed gut microbes in mice. And that made them gain ten percent of their body weight in two months, which researchers said was similar to about a 30 pound weight gain in a year for an average human. And then there’s one other one. There’s a woman and she needed new gut microbes to kill an infection she had; it’s called C. dif. and it was resistant to antibiotics. And uh, Mary, I don’t know, you may have heard of fecal transplants; it’s a way of changing the gut microbe community. I know it sounds a little gross.

MH: Yeah.

CB: But she had a transplant from her overweight daughter, teenage daughter. And so this is you know, it’s just a case study of one person, but she gained 40 pounds. She was eating and exercising the exact same and the only thing that changed was her gut microbes.

MH: Hold it, so…This woman gets a transplant of microbes from her daughter.

NT: And her daughter is overweight.

MH: And then she becomes overweight.

CB: Exactly, when the study was published it was 40 pounds that she wasn’t able to get off.

MH: Wow. What happened to her, do we know?

NT: She did beat the infection is the good news.

MH: Okay, so even if the calorie counts on our foods are exactly the right, which we know they are probably not. Chances are the amount of calories each of takes from that food varies, potentially quite a lot based on kinds of bacteria living in our guts. And by my count, this is strike three against the calorie.

MH: So what do you guys think? Should we just get rid of the calorie all together?

CB: That’s what Nicky and I keep talking about.

NT: That is the really interesting question. I mean, I kind of…I’m more revolutionary than Cynthia on this. I’m like it’s broken. You know our thought about this is -- is it the most helpful way to measure food? Calories were invented in a totally different era, in the 1800s and 1900s, and the primary concern then is that people need to get fed. Are they getting enough food, are they getting enough nutrition, are they not starving? Today, for many of us it’s completely the opposite problem. We have too many calories, we have too much food, we have different health challenges. And so maybe the calorie was right for that era, but something else is right for this era.

CB: But I do want to point out, when we were talking to the researchers they all came back to the fact that calories do matter and it’s really a matter of physics. If you’re burning a certain amount and you want to lose weight you have to take more in than you use up; it’s still true. The problem is that we don’t really know how many we are taking in. And it’s really hard to be exact about it; it’s almost impossible for someone to really count calories for themselves. And it’s almost more useful as this relative measurement.

MH: So we don’t know how many we are taking in, we don’t know how many we’re burning, but it’s still the best we’ve got.

CB: Yeah, pretty much.

NT: Kind of.

MH: It’s kind of depressing.

MH: Cynthia, Nicky you so much for coming on and telling us more about the calorie.

NT: Thank you, this was fun.

MH: Cynthia Graber and Nicola Twilley are the cohost of Gastropod. We have a link to their show on our website. Does this change the way you think about food or dieting? Tell us at OnlyHuman.org or tweet us @OnlyHuman.

Correction: This article initially included a quote by Cynthia Graber that said you should take in more than you burn to lose weight. This was a misspeak, and Graber meant the opposite.