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From “The New York Times,” I’m Sabrina Tavernise, and this is “The Daily.”

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A new study has found that nearly 3/4 of American adults are now obese or overweight. And there’s been growing concern among politicians, scientists, and consumers about one potential culprit —

— ultraprocessed food.

Today, my colleague, nutrition writer Alice Callahan, on how these foods came to be such a big part of what we eat and why that’s so hard to change.

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It’s Friday, December 13.

Alice Callahan, welcome to the show.

Thank you. It’s so good to be here, Sabrina.

So you cover nutrition for “The Times.” And you, as I understand, are uniquely qualified to have this conversation about ultraprocessed foods because you literally have a PhD in nutrition.

I do have a PhD in nutrition. That’s right. So, I started out in academia. I thought that I would be a nutrition scientist. But pretty soon after, I actually decided to transition to science writing because I really wanted to be in a position where I could read the science, talk to the scientists, and then be able to turn around and interpret it for everyday people who are trying to figure out what to eat.

And one of the things that we’ve seen in just the last few years in this field is a real change in the way we talk about food. When I was in graduate school, we were learning all about carbs and fats and protein and vitamins and minerals, and how we break these nutrients down and use them in our bodies. Nobody at that time was talking about how foods were processed. And now, just in the last few years, we’re seeing a lot of attention on how food processing might affect our health and especially this category of ultraprocessed foods.

And tell me about this category. What are ultraprocessed foods exactly?

So ultraprocessed foods are this giant category of products that include kind of anything edible that’s industrially produced; things that you can’t make in your own kitchen if you tried, because you wouldn’t be able to get the ingredients and you don’t have the machinery necessary to make that product.

OK, so these are foods that have really long lists of ingredients, the names of which you kind of don’t understand what they are. Right?

That’s right.

OK, Alice, I went to the grocery store this morning, knowing that you were going to come in and be recording with us. And we have some items here.

OK.

I don’t know if you can see this here. Do you see?

Ring Dings?

Ring Dings. Just a few ingredients — high fructose corn syrup, sodium aluminum phosphate, monocalcium phosphate, preservative sorbic acid, sodium caseinate, polysorbate 60, and dried eggs.

Oh, my goodness. Yeah, that’s definitely ultraprocessed. You knew that. [LAUGHS]

I did. You’re right. That’s why I pulled it off the shelf.

I’m just going to show you, here is Wonder Bread. “Monoglycidities?” Let’s see. Hold on a second. Sugar, calcium peroxide?

It’s — that sounds ultraprocessed to me, Sabrina.

OK, here’s one. Looked healthy to me, and I often eat these things. Yoplait Original, “made with real fruit,” Mountain Blueberry Yogurt. OK, it has blueberries, milk, sugar, gelatin, cornstarch, pectin, natural flavor, vitamin A acetate, and modified food starch.

Yes, so that unfortunately is also ultraprocessed.

Ugh! That is ultraprocessed. OK. So everything in my grocery cart is ultraprocessed, even the yogurt.

Pretty much. Yeah. So that’s one thing about this category, is that it’s so huge. And it includes lots of foods that we may think of and know are not very good for us, like soda and hot dogs and chips and cookies, but also these foods like flavored yogurts.

You can have an unprocessed or a non-ultraprocessed yogurt if it just has the milk and the bacteria starter culture in it. A plain yogurt would not be ultraprocessed. But once you add the flavorings and the various ingredients that give it that creamy texture, it becomes ultraprocessed.

A packaged big-brand whole wheat bread would also be ultraprocessed, probably because it has a few ingredients in it, like emulsifiers, that are important for the texture.

And Alice, what’s the universe here? How much of our food is ultraprocessed here in America?

Yeah, so here in the US, about 70 percent of our food supply would be classified as ultraprocessed.

70 percent? 7-0?

That’s right. Yeah.

OK. So here’s my question for you. Most people, I think, would acknowledge that ultraprocessed foods are kind of bad. Now, of course, you make the point that it’s a huge category, but lots of what’s in ultraprocessed foods isn’t really something that we think generally we should be putting a lot of into our bodies. But it’s everywhere. So why have these foods been allowed to proliferate like this? What is driving this kind of expansion of these foods?

So that’s a great question. I think part of the answer is a business story. There’s also a science part of it as well. I think the reason why these foods have come to dominate the marketplace is that they’re made to be really convenient, they’re shelf-stable, they’re pretty inexpensive.

We saw them starting to enter the scene, early 1900s, really take off post-World War II.

A lot of them allow us to create meals in just a few minutes. And so they’ve been very useful for people. And by the late 1980s —

— ultraprocessed foods were already about 60 percent of our food supply.

Wow. Already by the ‘80s, they were 60 percent.

Yeah. And if you grew up in the ‘80s —

— a lot of us can look back and say, like, yeah, these foods were around at that time.

But something about the foods also changed in the 1980s and ‘90s. And this is something that we’re just starting to understand.

What happened was that tobacco companies — RJ Reynolds, Philip Morris — bought up a lot of food companies. And they maybe did that because regulators were cracking down on the tobacco industry, and they were diversifying their holdings a little bit. But yeah, they started buying companies like Nabisco and Kraft.

And scientists have found that when they look at the food brands that were owned by tobacco companies, the foods that were coming out of those companies looked really different from the other brands that were made by other companies.

In what way?

So the tobacco-owned products were much more likely to be something that scientists call hyperpalatable.

And what’s hyperpalatable?

So this is a term that was defined by addiction scientists to describe a food that has high levels of at least two nutrients. It’s either high fat and high salt, or high carbohydrate and high salt, or high fat and high sugar, so these pairs of nutrients. Like you wouldn’t normally find a food in nature or an unprocessed food that is high in two of those nutrients at the same time.

And scientists think that when we eat a food that’s hyperpalatable, it just makes it harder for us to stop eating it. We want it more, and we reach back into the package of Oreos for another cookie. And not all ultraprocessed foods are hyperpalatable. These are two different terms, but they overlap a lot.

And what you see in the 1980s and 1990s is that more and more of these ultraprocessed foods were also hyperpalatable. And that seemed to be driven by the tobacco companies. They were maybe a little bit ahead of the other companies in cracking that hyperpalatability code. But by the 2010s, basically all of the food companies get on board and bring their products up to speed.

So tobacco companies kind of originally were the pioneers here, bringing us, it sounds like, highly addictive food, kind of like cigarettes.

Yeah, there do seem to be some parallels there.

And they take off, not just in the US, but all around the world.

We see more and more of these foods entering the food supply.

And meanwhile, obesity rates are also rising. So in the US, for example, our childhood obesity rates have tripled since the 1970s.

Tripled?

Right. So it’s become a huge problem. And we see the same thing happening in countries all around the world, although we may be a leader in this regard. And so this is where we turn from a story about the business of food to a story about health and science because scientists are alarmed.

They’re scrambling to figure out why people around the world are gaining weight. Is it that we’re not getting enough exercise? Or is it our nutrition? Are we consuming too many carbohydrates or too much fat or not enough protein?

But there’s this one scientist in Brazil, named Carlos Monteiro, who starts to look at this question a little bit differently. In his country, he notices that people are consuming less traditional foods like rice and beans, and more foods like instant noodles and sausages. And so in 2009, he is the one who actually coins this term, “ultraprocessed food,” and he creates a system to foods from unprocessed to ultraprocessed.

And so in creating this definition, Carlos Monteiro and his colleagues are now able to quantify how much of the food system is coming from these foods and how has it changed over time. And that allows them to study whether or not it’s linked to obesity. And they find indeed in Brazil, as ultraprocessed food consumption goes up, so does obesity.

Other scientists around the world are like, oh wow, this is an interesting way of looking at diet and health. And they start to see the same link between ultraprocessed foods and obesity, as well as other chronic conditions like type 2 diabetes and cardiovascular disease, some types of cancer.

And so this appears to be kind of a major breakthrough in our understanding of diet and health. But proving that ultraprocessed food is causing those health conditions turns out to be a lot trickier than you might imagine.

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Alice, I bit into my Ring Ding.

How is it?

(LAUGHING) It’s really good.

It is hyperpalatable, like uber hyper.

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We’ll be right back.

So, Alice, what do you mean when you said it was harder than you’d think to prove that ultraprocessed foods cause obesity and other health problems?

Well, this is the eternal challenge of studying nutrition and health. Right? You can observe a large number of people. You can look at how they eat, and you can look at what health conditions they develop or whether they develop obesity. But proving that it’s the food that causes those conditions is really challenging.

In other words, just because people are becoming more obese over time, and as a result, suffering from diseases like type 2 diabetes, that doesn’t necessarily mean that it’s the ultraprocessed foods that’s causing that obesity rise.

That’s exactly right. Diet is really complicated. And then food is just like one of the things that can affect our health, right? And you can imagine that people who rely more on ultraprocessed foods might also be the same people that are getting less sleep and maybe exercising less, or they’re under more stress, or they’re experiencing more poverty or discrimination or less access to health care. All of these other factors might contribute to someone’s health over the long term.

So, Alice, how do you isolate the driver of worse health, then? How do you go about doing that?

So for that, you really need a different kind of study. You need a clinical trial. In a perfect world, you can imagine if you took a large group of people and you randomly divided them into two groups and had one group consuming a diet full of ultraprocessed foods and another group consuming a diet full of unprocessed foods, and you would keep them all living in the same conditions and track them for years and see who develops obesity, who develops type 2 diabetes, that kind of study is obviously really hard to do over the decades that it takes to develop a chronic health condition.

Wait. You’re not really going to say, hey, 10,000 people, come live in my lab for 10 years, and I’m going to control everything, and you’re going to eat exactly the same thing as that guy?

That’s exactly right. What you can do, though, is a trial kind of like that, but for a much shorter amount of time. And so there was this small study conducted by a researcher named Kevin Hall. And what he did was recruit 20 adults to come and live at the National Institutes of Health for a month. And each of those study subjects, during their month-long stay at the NIH, spent two weeks consuming a diet that was made up of unprocessed foods and two weeks consuming a diet made up of ultraprocessed foods.

These diets, they were actually very carefully designed by research dietitians so that they were matched in the number of calories on the plate, the amount of carbohydrates, the amount of fat, the amount of sugar, the amount of sodium. So they really wanted to try to isolate this ultraprocessed factor from the actual nutrition provided in these meals. And they told the study participants that they could consume as much or as little as they wanted of these foods that were placed in front of them.

So what happened? What did the study end up finding?

Well, I think I should say first, too, that Kevin Hall went into this study thinking that they would find no difference in how much people consumed or whether or not they gained weight during their time at the NIH. Because the diets were so carefully matched for nutrition, he thought that was the thing that really mattered, and there wasn’t really anything to this ultraprocessed concept affecting people’s food consumption or health.

But what he found shocked him and shocked, I think, a lot of people. He found that while people were on the ultraprocessed diet, they gained 2 pounds in two weeks, and they ate 500 more calories per day than they did when they were on the unprocessed diet without even realizing it. Like, they had no idea that they had consumed more food.

So it’s a short-term study. You don’t know if that amount of overconsumption of calories and weight gain might continue if the study went longer than that. But in that short amount of time, you see this really striking difference in how people responded to these very different types of meals. It is very clear that people ate more calories than they needed when they were served these ultraprocessed meals.

OK, so in a controlled environment, in the perfect scenario, which Kevin Hall created, it is true that people do eat more calories and do gain weight from these ultraprocessed foods. But do we know exactly why they do, Alice?

We don’t. Kevin Hall is currently conducting a second trial to try to tease that out, and he’s testing a few different ideas. One goes back to that hyperpalatability concept. So maybe it’s the fact that these foods are more likely to have these pairs of nutrients that light up our brains in rewarding ways and want us to come back and consume more.

Another is that ultraprocessed foods tend to pack more calories in per bite, and so you might just subconsciously consume more of them because they take up less space in your gut than an unprocessed food. If you can make ultraprocessed foods that aren’t hyperpalatable and don’t pack as many calories in per bite, then people do seem to consume less of them. So that’s what’s giving us some hints as to what is going on.

These foods are being designed to make us want to eat them and want to eat more of them.

Yeah. It certainly seems to be the case. And there’s another thing about ultraprocessed foods that I think scientists worry about, and many of us worry about, too, is that they contain all of these ingredients that we can’t pronounce. And it turns out many of them, we don’t have a great grasp on how they affect our bodies.

We have some small studies that show, for example, that artificial food dyes maybe affect children’s behavior. Artificial sweeteners maybe change our microbiomes. Some of these other ingredients maybe increase inflammation levels in our bodies. This is really emerging science, but it kind of adds to the accumulated concerns about these industrially made foods.

OK. You should have told me that before the Ring Ding.

[LAUGHS]: Sorry, Sabrina.

OK, so we know that ultraprocessed foods can cause weight gain, at least according to this small study, and we’re starting to get more research to understand why that happens. But why has it taken so long to get to this point?

That’s another great question. I mean, nutrition science has been chronically kind of notoriously underfunded by the government. So a lot of nutrition research actually ends up being sponsored by food companies and industry groups themselves. You can imagine that this has not been top of the list for food companies to investigate these effects.

In the United States, about 5 percent of the National Institutes of Health budget goes towards nutrition research. And I think there’s a growing recognition that we may need to invest more in understanding this issue if we’re going to wrap our heads around what the problem is with these foods and what we could do about it.

What does that growing recognition look like? What’s happening?

Well, I think scientists will always say, we need more research. But we’re seeing countries around the world who are saying, we know enough to start taking action, and we can’t really afford to just let things continue as they are. So we’re seeing countries, for example, putting prominent warning labels on ultraprocessed foods, or at least certain ultraprocessed foods, like big stop signs that clearly say on the front of the package, this is not a healthy choice.

We’re seeing countries limit marketing of ultraprocessed foods to children. We’re seeing them get ultraprocessed foods out of school meals. But here in the United States, when I talk to experts about these types of policies, a couple years ago, they said it seems unlikely that a lot of those policies would really take off in the United States because we have a very strong food lobby.

But things are really shifting, I think, in this conversation. We saw it during the presidential campaign. Robert F. Kennedy Jr. campaigned pretty heavily for himself and then for Trump on this idea of making America healthy again. And he talked a lot about ultraprocessed foods and the effects that they’re having on children’s health. And I think you saw that resonate with a lot of people. And politicians on both sides of the aisle are taking an interest in this.

There was a hearing in the Senate last week where there were no senators who defended Big Food. It was kind of like, yeah, ultraprocessed foods are a problem, and we need to change something in this country.

OK, Alice, here’s the part in the podcast where I ask you how you think about these foods because you’re the expert. I want to probably try to avoid a lot of these foods, and I want to know how you think about doing that, given that they’re kind of everywhere.

Yeah, I think it’s really tough. And we are, again, talking about 70 percent of the food supply. And a lot of these foods I, as a parent, do rely on, things like breakfast cereal, Honey Nut Cheerios, my kids eat occasionally.

But here’s what I would say. We’re still learning a lot. And one of the things we really don’t know is whether or not all of these foods in this huge category of ultraprocessed foods are bad for us. Like, just because they’re industrially produced, are they unhealthy? Probably not. And we’re talking about a category that includes everything from soda to whole wheat bread.

So the way I think about them is I’m looking at sort of degrees of ultraprocessing. Like if it’s a whole wheat bread, that the only thing that makes it ultraprocessed is the inclusion of one food additive that I don’t recognize, I’m less concerned about that. I think try to sort out the worst offenders, which are sugary drinks, ultraprocessed meats like hot dogs and chicken nuggets, and then foods that obviously don’t provide us with very much nutrition and are difficult to stop eating. Those are my kind of red flags for the ultraprocessed foods I’m going to try to avoid.

Thinking about the future of this problem, Alice, I wonder if an analogy is the tobacco companies in the beginning of the conversation and the cigarette industry, right? That back in the beginning, the industry was incredibly well-funded. It was very difficult for scientists to prove that cigarettes were, in fact, bad for you. But eventually, they did, and eventually, they were regulated. And I wonder in some way if ultraprocessed food might also follow that same trajectory, but just be at the beginning of it right now.

Yeah, I think that’s quite possible. I’m seeing more and more addiction scientists who traditionally have studied substances like tobacco and alcohol now turning their attention to foods —

Interesting.

— and trying to really understand the potentially addictive nature of foods. But it’s a bit harder with food, right? Because we don’t need cigarettes, and we can isolate from cigarettes the addictive substance, which is nicotine.

Food is different. Like, we all need to eat, and ultraprocessed foods are convenient and feed many of us with the calories that we need every day. So proving that there’s an addictive nature to some foods is a bit more challenging. But there are a lot of scientists now who have taken an interest in that and are working on it. So I think we may be moving in that direction.

And there is a growing sense that this helps us make sense of the problem that we’re facing. This rise in obesity, for a long time it’s been talked about as a personal failing, like people are not exercising enough and they’re eating too much. And if we’re talking about living in an environment where we’re surrounded by foods that are difficult to stop eating because they’ve been engineered that way, it sort of changes the way you think about the problem and opens the door, I think, for more solutions.

Like if we could change the environment so that it’s not so saturated with foods that are hard to stop eating, then we may have a chance of turning the tide on obesity.

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Alice, thank you.

Thank you, Sabrina.

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We’ll be right back.

Here’s what else you should know today. On Thursday, President Biden said that he was commuting the sentences of nearly 1,500 people and pardoning 39 people in a sweeping act of clemency during his final weeks in office. The White House said that it was the largest number of commutations by an American president in a single day. The commutations affect those who have been released from prison and placed in home confinement during the coronavirus pandemic. The pardons are for people who were convicted of nonviolent crimes, including drug offenses.

As a Senator, Biden had championed a 1994 crime bill that many experts say fueled mass incarceration. He has since expressed regret for supporting that legislation, and he committed during the 2020 campaign to addressing the long drug sentences that resulted. The announcement came two weeks after Biden issued a pardon for his son, Hunter, a decision that was harshly criticized by both Republicans and Democrats.

A quick reminder to catch a new episode of “The Interview” right here, tomorrow. This week, Lulu Garcia-Navarro talks with travel guru Rick Steves about why he spent his life encouraging Americans to get outside their comfort zones.

Today’s episode was produced by Alex Stern, Sydney Harper, and Rikki Novetsky, with help from Olivia Natt and Michael Simon Johnson. It was edited by Lisa Chow and Chris Haxel, contains original music by Dan Powell and Marion Lozano, and was engineered by Chris Wood. Our theme music is by Jim Brunberg and Ben Landsverk of Wonderly.

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That’s it for “The Daily.” I’m Sabrina Tavernise. See you on Monday.