Clearing Up the Calorie: The Science of Nutrition, with Marion Nestle

May 11, 2015

When over one-third of American adults are obese, it’s no wonder that our culture is deluged with fad diets and alleged miracle supplements. Everyone is looking for the easiest way to obtain and maintain health but it’s no small task in the midst of a whirlwind of conflicting information. And what the heck is a calorie anyway? It may be that the easiest fix is to look at what science tells us about the kinds of foods best fuel our bodies.

This week on Point of Inquiry, Lindsay Beyerstein takes a closer look at what science tells us about our diets as she talks with nutritionist and author of Why Calories Count, Marion Nestle. She’s the Paulette Goddard Professor of Nutrition, Food Studies, and Public Health at New York University and works extensively to research and educate what our bodies do and don’t need to work their best.

This is point of inquiry for Monday, May 11th, 2015. 

Hello and welcome to a point of inquiry. A production of the Center for Inquiry. I’m your host, Lindsay Beyerstein, and my guest today is the most famous nutritionist since and tell kids she could squish Dean Ornish like a grape or crush Dr. Adkins like a Chris macaroon. She makes Gary Taubes and the paleo tribe nervous. Marion Nestle is a professor at NYU. She has a p h d in biochemistry and a master’s degree in public health. She’s the author of several books, including Food, Politics, Safe Food and What to Eat. We’re here today to talk about her most recent book co-written with Nalden Machine. Why Calories Count. A book about the science of calories, dieting and weight loss. Now, Marion, you’ve written that moderation is the central nutritional concern. What do you mean by that? 

All moderation that’s always spoken with some degree of irony because it’s so difficult to define. And in fact, somebody once did a study of what nutritionists thought moderation meant. No. Two were alike. But basically, it means eating a lot of the basic tenets of healthy eating are eating a wide variety of foods. All different kinds of foods, change them day to day, constantly explore new ones, but always eating them in amounts that aren’t good and make you put on weight. 

And from a scientific perspective, what exactly are calories? 

Well, calories are a scientific concept and then an intangible one at that. But they describe the energy in the body. They’re measure of energy just the way temperature is and very much the same kind of thing. It’s analogous to temperature. It’s not something that you can sorry. I mean, a thermometer will do it for you. And in the case of calories, a scale will do it for you. 

Can you talk a bit about the history of the concept of the calorie? How scientists came to understand the energy value of our food? 

Well, it goes back as far as written records. I mean, from the very, very beginning of written records, Aristotle, for example, we too, we see that philosophers and people who were thinking about these kinds of things were trying to disarm. More bodies were warm. What made bodies warm? I mean, they knew that fire cooked food and they knew that fire could warm up houses, but they couldn’t figure out what kept bodies warm. And that’s where they began looking to see into looking into the concepts of the energy, because that’s calories are what keep us warm. There’s a fuel for the body. And in the same way that burning is fuel for keeping us warm in other ways. 

Can you tell us a bit about Dr. Atwater, the scientist whom you dedicated the book? 

Yeah, he was an absolutely amazing scientists working for the Department of Agriculture in the late 80s, 90s. And everything we know about calories was that he discovered he was very interested in measuring them. He was interested in measuring the number of calories in different kinds of foods. The number of calories that people aid in order to maintain their weight. The number of calories they expended in physical activity. And pretty much everything that he discovered back in the eighteen eighties has held up remarkably well, even with much fancier science since then. And I was just in doing research for this book, I was just awestruck at the quality of the science, the rigor of it, and the extraordinary number of experiments that he did and how carefully he did them. 

He was a government scientist, right? He was working, yeah. 

He was working for the Department of Agriculture. Who knew? 

And can you talk a bit about the work that he did, differentiate between what happens when you burn food and bomb calorimeter versus what happens when food is burned in the human body? 

Well, he was interested in finding out and measuring the number of calories that were given off when food was burned to completion. And what was called the bomb calorimeter. And it was possible to measure that number of calories by measuring the change in a temperature of water that surrounded the vessel in which the food was being burned. And it was completely analogous to what goes on in the body. So if the food in the calorimeter outside the body produced 100 calories, it was going to produce 100 calories in the body unless there was protein in the food. In which case some of the protein is lost and excreted. So you would have to correct for that. But for carbohydrate and fat, what’s the outside the body and what’s inside the body? Remarkably close. 

So when you read a nutrition label today and you know, it turns out that fat has nine calories per gram. That’s that’s Dr. Atwater’s work that we’re looking at basically from the eighteen nineties. 

That was his work. Yeah. I mean, he did the thing then then he measured the number of calories per gram of protein, fat and carbohydrates from lots and lots of different sources and came up with the average values of four. Four. Actually he was using a point one that they rounded it off to nine at some point. But the four calories per gram for protein and carbohydrate and nine calories per gram fat derived from his work. And there’s been very, very little change in that since then. 

And the idea is that you get more energy if you just burn it in a calorimeter for these things. But from some of the nutrients, you actually get less in the human body because some of it is is being wasted. 

Well, it’s either not digested, so it’s excreted or it’s given off as heat in some way. And it’s and there are losses along the way. But the measurements are pretty close. They’re close enough. You can’t really without using very, very fancy equipment, you can’t really guess the number of calories in food and you can’t tell how many calories you’re using in the body expanding in the body. It’s it’s not something that individuals can do. And it requires scientific measurement with special devices. You have to weigh the food. You have to do all these calculations. And I killed him. Even though my book is called Why Calories Count, It Nowhere recommends that anybody try to count calories because you can’t do it accurately. 

Have the met the takeaway I got from the book was that nobody really has any idea. Not the people who fill out surveys, not people who measure and weigh everything that goes into their mouths. Why are we so misinformed about what we’re taking into our own bodies despite our best efforts? 

Oh, I don’t see it as misinformation at all. I see it as we eat. And the body has internal signals which work in many people that tell you when you’re full and when you’ve had enough to eat and tell you when you’re hungry. And that’s really all you need to know. It’s impossible to know how many calories are in the food you’re eating and how many calories you’re expending in need without using a scale and weighing yourself. That’s still the best way to do it. If your weight’s not changing your balancing calorie intake and expenditure, relax, enjoy it. Would you, like, have fun? If you’re gaining weight, it means you’re eating more calories than you need for the amount that you’re expending. But to try to do that on a daily basis, there are people who claim that they can do it. I certainly can’t. I’m not one of them. I have no idea how many calories are in the food I’m eating, particularly if I buy it in a restaurant or if I get takeout or something like that. I don’t know how they made that food. 

Was it for food politics that you actually had restaurant dishes analyzed and compared to your best estimate as a trained nutritionist for what was in those dishes to what came back from the lab and found some really surprising things. 

Now, I talked about that in, I believe, my book, What to Eat. That was it that was discussed in that book. And, you know, in general, what you see on a food label makes sense. What is in restaurants depends completely on how much the food weighs. 

And you have no way of doing that unless you go into a restaurant with a scale and weigh everything that you’re eating. And that’s usually how people do things. 

It used to be thought that obese people didn’t eat significantly more than average weight, people on average. But you mentioned that the scientific consensus has changed on that. How has it changed? What kind of evidence can to undermine that former view? 

Well, if you if you ask people what they eat, they have no idea and typically underestimate it if you watch what they eat. You see that they’re eating much more than they think they do. And this is true of everybody across the board. So to rely on people’s self report on what they eat, it makes for very bad science. 

Can you talk a little bit about the doubly labeled water method for figuring out how much people are really ingesting? 

Yeah, I can only say that it is a method for examining the amount of carbon dioxide that you excrete through your lungs. And that is a measure of the number of calories that you are expending. And if you use this doubly labeled water technique, you can find out how many calories people actually are expending. And that that reflects the number of calories that they’re eating. And you get a much better idea of work requirements that way. When you compare caloric requirements from doubly labeled water to the number of calories that people say they’re eating to maintain weight. There’s usually about a thousand calories a day difference. 

The doubly labeled water indicates that people require many more calories. And they say they’re eating, but they’re actually eating that many or else they would be losing weight. 

Colloquially, we talk about metabolism, having a fast metabolism or having a slow metabolism. How do scientists think about metabolism? 

Well, metabolism scientists don’t think about it very much. I don’t think very many people is studying metabolism anymore. But it’s a measure of the amount of energy that you’re expending over time under a highly defined conditions. And what those experiments show is that most of the calories that you use on a day to day basis are used for maintaining basic life function, keeping your heart eating, keeping you warm, keeping your muscles moving or able to move and so forth. And that physical activity is another big component on top of that. And so that’s why it what’s one of the reasons why it’s so important to be physically active is it burns calories and keeps your muscles trim and in better shape and using calories more efficiently. So, you know, the basic rules about diet and health are plenty of fruits and vegetables and be active and don’t eat too much junk food. And that really takes care of it for a lot of people. 

This dubious diet books that claim that calories from alcohol are somehow more likely to contribute to weight gain in themselves because they’re metabolized differently or the order in which the fuel is processed, is there any truth to that? 

Well, there may be to some extent, but most of the research shows that the calories and alcohol were just like the calories in anything else, calories or calories. The body really doesn’t care where the calories come from. From the standpoint of weight, it cares a lot about where the calories come from, from the standpoint of health. 

And yet in the book, you say that there’s still this live scientific controversy over whether the relative contributions of how much we eat versus what we eat in terms of weight maintenance or weight loss. Can you tell us a bit about the extent to which that controversy still exists? 

Well, it does still exist. And one of the reasons why it exists is that the experiments are very hard to do. I mean, if you think about it for a while, the issue is over carbohydrates, whether if you give people a lot of sugar that the body will put on fat at a greater rate than it would if you gave people a lot of fat, for example. I’m of the opinion based on the research that I’ve done that from the standpoint of weight, calories or calories. And if you overeat calories relative to expenditure, you’re going to gain weight. But think about how hard those experiments would be to do. You would need to put a statistically significant number of people on a diet that had a lot of sugar in it or they didn’t have a lot of sugar in it. And you would have to measure every single thing they aid and drank during that period. You’d have to measure their caloric expenditure. You’d have to monitor the weight very closely and make sure they didn’t cheat on their diets. That would be really hard to do. But there is one such study in progress, and I believe it’s being done in a metabolic ward where the dietary conditions can be controlled. And I’m very interested to see the results of this, but they’re not out yet, whereas the study being done, I don’t know whether it being done at something that was organized by Gary tells. 

So you don’t give a lot of credence to Gary Taubes idea that you can fine tune the macro nutrients in your diet and load on protein or give yourself an edge at weight loss. 

I haven’t seen data that would support that. It may be that for certain people, certain kinds of diets are more satiating than others. And so if you eat those kinds of diets, you lose weight. But nobody measures the calories under those circumstances. And I would be willing to bet that if you’re losing weight, you’re eating fewer calories. 

We’re often warned that simply reducing the number of calories we eat brings on some kind of starvation state, that you can somehow permanently break your metabolism by going on a calorie restricted diet. So any basis to those fears? 

No. Car metabolism, fights, starvation. I mean, the entire basis of metabolism is to make sure that you have enough sugar glucose in particular to get into your brain and keep your brain functioning. And the if you’re not eating enough to make sure that you get 200 grams a day of sugar in your brain, the body goes through lots and lots of contortions to make you plenty uncomfortable so that you do something in order to eat and make sure that you’ve got enough carbohydrates for your brain. So one of the reasons why losing weight is so difficult is because of all these compensatory mechanisms come into play and fight weight loss. Bodies do not like to lose weight. And so, yeah. Diet is hard. 

So it’s true that if you go on a long term semi starvation regimen, your basal metabolic rate will decline while you’re actually food deprived, right? 

Absolutely. Absolutely. 

But does it recover? I mean, accounting for whatever lean body mass that you lost? Oh, yeah. 

The minute you start eating and it comes back. 

So it’s a myth that when diet books say, oh, you can break your metabolism by dieting, I’m not aware that that’s the case. 

So what you can do is get used to a lower level of calorie intake and stabilize your weight at a certain level. But if you’re trying to continually lose weight, you’re fighting your own metabolism. 

It’s very hard to do when we cut back our intake below our energy needs and we start to lose weight. We lose some mixture of fat and muscle. Right. 

Oh, absolutely. Yeah, you lose everything. 

Some diet books claim that by following a particular dietary prescription, you can eliminate the loss of lean body mass. Why you lose fat. Is there anything that can actually do that? 

Yeah, you can slow it down. You can’t eliminate it completely. And these are diets that replace fat. But don’t you know these are low carbohydrate diets that remove carbohydrates? If you remove carbohydrates from a weight loss diet. Remember, you have to have 200 grams a day of carbohydrate for your brain. So you have to get that carbohydrates in some place. You can’t get it from fat because very, very little of fat can be synthesized into carbohydrate in the body. So you’re breaking down protein and you don’t want to break down protein because you need muscles and protein structures in your body to keep functioning. So in order to prevent that, you go on what is called a protein sparing fast in which you give people lots more protein. Will the protein in the diet is going to then be broken down to carbohydrate? Because it has to be because you need that carbohydrate for your brain. And that will spare the protein breakdown to some extent. 

But protein will still be breaking down and long term starvation is very bad for health. 

So Gary Tab’s really likes to sing the praises of ketosis. What is ketosis and why is it supposedly good for us? 

Well, I don’t think it’s supposedly good for us. But ketosis is the way in which the body keeps fuel in the brain. In the absence of carbohydrate. So if you’ve cut out carbohydrate at your end, you have very, very literally your diet. And you’ve got protein breaking down, fat breaking down in order to try to keep your calorie needs of the fat will break down two compounds called ketones and the brain will adapt, teasing, ketones instead of glucose as fuel for the brain. And that will break down fat. But the minute you start using carbohydrate again, that’s going to reverse. And you don’t want to be in ketosis for too long, it smells bad. 

For one thing, that’s the sort of acetone like smell that people get on their breath. 

Yeah, it makes for very bad breath, among other things. It’s it’s not a good long term strategy. 

And there’s nothing about ketosis that makes you lose more fat or is there something about ketosis? Gary Taub seems to imply good calories, bad calories that you end up losing more fat because of it. 

Well, you may because because some of it is being used to replace the glucose that has to go to the brain. But it’s not a long term strategy that most people can stay with. It’s a starvation strategy and starvation is not good for health. 

What would happen if somebody were to eat a key topic diet for the rest of their life? Physiologically, would they get sick? 

Oh, I’m not aware that anybody’s ever done that. I mean, usually when people are in ketosis, it’s because they’re starving. 

And at some point they don’t survive in terms of body composition, a lot of exercise manuals claim that if you add a pound of lean body mass through resistance training or whatever, that it burns a certain number of calories a day. And I’ve read estimates that vary from 25 to 100. What’s the actual consensus about how much a pound of muscle burns, apart from just the work of carrying an extra pound of stuff on your body? 

Yeah, I actually don’t know those figures. Sorry. 

Just thought I’d ask. I’ve been curious about that for a long time. Yeah. 

No, I mean, I think I think there is that lean muscle tissue metabolizes at a faster rate than fatty tissue. But I don’t know what the exact numbers are. 

Do you have any opinions about the health at any size movement and its teachings? 

Yeah, I understand it. And I. I’m opposed to stigmatizing people who are overweight. And this movement has come about as a way to say that not everybody who’s overweight is unhealthy. But in fact, the research shows that being overweight has long term consequences in a much more prominent way than has been known in the past. And the most recent research I’ve shown shows that overweight raises the risk for chronic disease and chronic disease. Biological indicators like high serum cholesterol or high blood glucose or high blood pressure. And that even though at point, A, you might not see the increased risk if you wait six months or a year or two years, you will start to see it as a much higher probability. 

For listeners who don’t know, the health at any size movement is one that teaches that if you’re eating a good diet and you’re exercising, that it’s possible to be healthy regardless of what your weight is. 

I think. I think possible. Yes. Probable, no. 

So there might be a subset of people who are at a certain weight doing everything right and all their blood numbers are coming. That good cholesterol, good blood pressure would trigger all that stuff. So if you’re one of those people, can you say, OK, I guess my body was just meant to be the size? 

No, because the research shows that even if you’re fine now, the probability this is all about probability and chance, the probability of your developing chronic disease risk factors is still higher than from someone who’s not overweight. 

You talk a bit in the book about toxic food environment that we live in. What are some of the features that are most insidious in terms of sabotaging people trying to maintain a moderate calorie intake? 

Oh, it has to do with the availability of cheap foods and the widespread availability and the marketing of that food so that if food is available, you’re going to eat it. Food is cheap. You’re going to buy it. And it’s served in very large quantities. And the larger the amount of food that you’re served, the more you’re going to eat of it. Those are all environmental factors that promote unhealthy diets and eating more calories than you need or want. 

Some nutritionists recommended increasing food frequency, so grazing instead of eating large meals. Is there any? It seems like that’s good for the snack industry. But is it is there any evidence that there’s any weight maintenance benefit to spreading out your calories more over the course of the day? 

Yeah, I’m I think for some individuals, it may make a difference that if they spread the calories out over the day, they’ll eat fewer than if they eat three big meals. But I think there are also people who every time there’s an easy occasion, we’ll take in more calories than they would otherwise. And so those spreading it out over the day would add up to more calories. So I think this is a very individual thing. 

How do you feel about these currently popular intermittent fasting regimens that everybody’s talking about online, intermittent fasting oil? 

I mean, that’s what you do when you only two meals a day. Yeah. You’re intermittently fasting. 

Do you think there any unique metabolic benefits to that sort of thing? 

There may or may not. It depends on what else you’re doing. It doesn’t do you any good to intermittently fast if you’re going to gorge during the times when you actually eat. And really, it’s the overall intake that matters, although individuals may vary in the way they respond to amount’s food. 

So some people are find it easier to regulate their overall caloric intake if they eat moderately at regular intervals, whereas other people find it easier to just take it in fewer, larger chunks that are easier to keep track of. 

Yeah. I mean, for me, I like to eat when I’m hungry and not eat every wise. 

Seems like good advice. 

Yeah. Sighs If you can do it. But if you’re presented with food all the time, it’s much harder. 

In the book, you talk about the food industry using all kinds of nutritional claims as marketing hype and how those claims service calorie distracters. 

Yes, if you see that a food is low in trans fat, low in fat. What are some of the other ones that we see organic? That’s a good one. People think that organic foods are having fewer calories. There’s research that demonstrates that. And in fact, people think that any food that has a health claim on has fewer calories than the same food that doesn’t have a health claim. And marketers know this. And this appeals to people at some subconscious level. So you don’t even realize that you’re falling for this. But everybody does. 

So people actually will therefore possibly eat more foods that have health claims on them than they would have the same food with nothing on the label. 

I mean, it’s healthiness, but they certainly might. Again, this varies of individuals, but yes, certainly. 

So you think that the food industry has a vested interest in keeping us distracted with all kinds of superficial health claims that don’t really add up to much? 

Yeah. The food industry has only one purpose, only one, and that’s to sell food. How they do it depends a lot on the particular industry. But that’s their purpose. And to understand what the food industry does in any other way, I think is to misunderstand the situation. Their purpose is to sell food. If health claims sell food, they will use health claims. If large portions sell food, they will use large portions. If putting food everywhere encourages food sales. They will put food everywhere because their job is to sell more food. And your job as an individual is to make choices among the choices that are available to you of healthier choices. And so you’re exercising your personal responsibility in this social and economic and political environment that is completely set up to sell you more food than you need or want or necessarily want. So it’s very, very difficult for individuals to exercise healthy choices in this situation. 

You mentioned that the calories available for people eating those states have increased dramatically. Where did the excess come from? What are we producing more now than before? 

Well, the farm policy changed in the 1970s. Our agricultural policy changed from a policy that paid farmers not to grow food to a policy that paid farmers to grow as much as a commodity producers. I’m talking about to grow as much food as they possibly could. And as a result of that, they expanded the amount of land that was being used to grow corn and soybeans and other kinds of commodities. And the number of calories in the food supply increased. And then food companies had to sell it food. You know, if you have food available, you’ve got to sell it. So it went from 30, 200 calories per capita, which was already a lot in 1980 to about 4000 calories per capita in 2000. And that’s roughly twice what the public needs. Every man, woman and child is what per capita means, and that’s roughly twice what the population needs. So food comes, the Flins is hugely competitive. And that’s why there’s so much waste in the food system as well. 

Do you think that we should think about changing the farm policy back to the old paying farmers not to grow things? 

Well, I think we should have an agricultural policy that’s linked to health policy where the people who are looking at agricultural policy start thinking about how we could produce healthier foods at lower cost and maybe unhealthier foods at higher costs instead of the other way around, which is what we have now. 

And farmers are there growing corn and soy, but not like corn on the cob is simply not growing broccoli and other. 

No, I know it’s animal feed. 

So this is linked to the meat industry. A lot of. 

Absolutely. Yeah. Sure. 

And have real prices for meat. What real prices for meat been doing since the 70s as meat getting relatively cheaper. 

Um, depends. Yeah. I mean, to some extent, yes, we’re eating less meat, less red meat than we used to reading more chicken and beef is very price dependent. And so they’ve worked very hard to keep the price down. 

Do you see that as a nutritional when we’re eating more chicken? 

It’s an impasse. And what we really want is to warn people to being more plant based foods, fruits, vegetables, grains, beans and those kinds of foods. And you want a food supply in which people are getting a much larger percentage of their calories from plant foods than they are from animal foods. 

What are some policies that could help push our diets in that direction? 

Well, we subsidize corn and soybeans. We could subsidize the production of fruits and vegetables. That would be a change. That would be one way to do it. To reduce the cost of index. Cost of fruits and vegetables has increased enormously since 1980, whereas the index price of processed foods has gone down quite a lot. So we would like to see I mean, we could do policies that reverse that. 

So you’re saying that in real dollars it’s more expensive to buy a pound of apples now than it was 1970 adjusted for inflation? 

Yeah, I agree. Yeah, absolutely. Usually the figures start at 1980, which is when all the changes took place. But yes, that’s the case. Fresh fruits and vegetables have gone up by about 40 percent. 

That’s amazing. Beer, butter and sodas gone down by about the same amount. 

Were you in favor of Mayor Bloomberg’s policy before it got shut down of portion caps on large sodas? 

I thought it was a really good idea because we eat what’s in front of us and there’s tons of research that shows that portion size influences what people eat, the amount that people eat. And I’ll always laughing when I say that if I had one thing I could teach the American people, it would be that larger portions have more calories. I came and say it without laughing. But I had this idea that you could cap the size of sodas and 16 ounces. And people who wanted to have more could have more. But at least nobody would have more than 16 ounces in front of them at any one time. I was up at 16 ounces was a lot. It’s nearly 50 grams of sugars, which is about what’s recommended for an entire day. And it seems like a lot to me, but it was shut down immediately on the nanny state argument that we don’t we don’t want government telling us what to eat, as if government isn’t already telling us what these system would just be a change. And people felt that this was taking their freewill away. I think it was a interesting idea, but it was presented very badly. 

So the idea was they were interfering with the sacred relationship between God, the consumer and Coca-Cola. 

Maybe, I would imagine, yes, there’s a very good history of Coca-Cola called from for God love. Oh, for God country and Coca-Cola. Yes. 

Any other tips that you have for consumers in terms of what they should be doing in order to eat a healthy diet? 

Well, I think it’s really simple. It really is is in a variety of foods. Lots of lots of foods studied too much of them. Make sure you have plenty of plant foods in your diet. Don’t eat too much junk food. It’s really that simple. And if you’re worried about weight, get scale and monitor your weight on the scale of the weight not changing. You’re doing just fine. You don’t have to worry about it. 

Thank you so much for coming on the show. It’s been a fascinating discussion. 

Thank you. It’s been a pleasure. 

Four more points of inquiry follows on Twitter at point of inquiry. And like us on Facebook, at Facebook, dot com backslash point of inquiry. 

Lindsay Beyerstein

Lindsay Beyerstein

Lindsay Beyerstein is an award-winning investigative journalist and In These Times staff writer who writes the blog Duly Noted. Her stories have appeared in Newsweek, Salon, Slate, The NationMs. Magazine, and other publications. Her photographs have been published in the Wall Street Journal and the New York Times’ City Room. She also blogs at The Hillman Blog (, a publication of the Sidney Hillman Foundation, a non-profit that honors journalism in the public interest.