What Are Ultra-Processed Foods and What Are They Doing to Us?

**Brian Lehrer** (0:10)
Brian Lehrer on WNYC.
Now we begin our annual WNYC Brian Lehrer Show Health Convening. It's about a 90-minute special that we do once a year on a major public health topic with support from the Alfred P. Sloan Foundation as an opportunity for health care experts and practitioners to inform WNYC's health reporting and inform you all as listeners. Today, our health convening takes on ultra-processed foods. What's the actual science about what makes a food ultra-processed, what health risks are actually associated with different kinds. One interesting finding from a researcher who will join us a little later is there seems to be a big gender difference in the colorectal cancer risk from a certain category of ultra-processed foods. She'll explain why women seem more susceptible and what that category of foods is. And we'll have former FDA Commissioner David Kessler, who's proposing specific new ways to regulate them and get his take on whether RFK Jr. just talks tough on ultra-processed food corporations or is actually doing anything as Health and Human Services Secretary. But we start with some of the basic science of ultra-processed foods with a leading expert in the field, Dr. Kevin Hall, former senior investigator at the National Institutes of Health, the NIH, a health and diet expert who had done some seminal research in ultra-processed foods and disease. He also, by the way, took early retirement from the NIH last year at age 54, because he said the RFK Jr. administration was censoring him. We'll get into some of that, but more of the science. Dr. Hall, thanks for coming on. Welcome to WNYC.

**Kevin Hall** (1:52)
Thanks for having me.

**Brian Lehrer** (1:54)
I think we should start with the definition. What are ultra-processed foods? How do you use the term?

**Kevin Hall** (2:00)
Right. Well, it's actually a topic that's fraught with a lot of debate right now. It's a real question about whether or not some of the debate is really trying to prolong the discussion so that the food industry can skirt by with having some of the unhealthy foods on the market, or whether there's real scientific debate about this topic.
The vast majority of studies have used something called the Nova Categorization System, which was developed by Carlos Monteiro's team in Brazil. It basically decides to group foods into four different categories. The minimally processed food category is group one. That's the typical fruits and vegetables and fresh meat and eggs and things like that that you would typically think of as quote unquote real foods. There's a second category, category two, which is processed culinary ingredients. Those are the things that you typically don't eat on your own. That's like the table sugar and cooking oils and things like that. Then there's category three, which is basically combinations of category one and category two foods, as you would typically prepare them in a home kitchen. Then there's the fourth category, which is labeled ultra-processed foods. It could be a category by exclusion. If it's not one of the first three categories, it belongs there, but it also has its own definition and basically is operationalized by ingredients or processes that are typically not used in home kitchens or restaurants.
The kinds of additives and flavorants and cosmetic things that are, and preservatives that are sometimes added to packaged foods that prolong their shelf life and also lead to potentially some negative health consequences.

**Brian Lehrer** (3:48)
So would you describe the landmark study that you conducted in 2019, described by the NIH at the time, as the first randomized controlled trial on the topic. I see that it was small, just 20 healthy subjects in short term, just one month. But tell us about that study. How did you group the participants? What did they eat? And what do you think you may have established?

**Kevin Hall** (4:10)
Yeah, sure. So this was, it was a very small sort of mechanistic study to try to understand, is there something about ultra-processed foods per se, that might be driving excess calorie intake, which is kind of on the pathway to weight gain and obesity. And what we did was we designed two sets of diets, where the nutrients were matched between them.
Not all the nutrients, but the typical players, the calories, the carbs, the fat, the protein, the sugar, the fiber, those kinds of things that we often think of as either health promoting or health deteriorating. These were matched between two diets that we had our cooks and our dieticians design. But in one case, all those foods came, or 80 percent of the calories came from ultra processed foods, that category four foods that we talked about in the NOVA system. And in the other case, 80 percent of calories came from minimally processed foods, category one, and no ultra processed foods. And we basically had people come to live with us in our research center at the NIH, to complete control over their environments. And for one month, continuously, they spent with us. And we either gave them for the first two weeks, the ultra processed diet, as followed by the minimally processed diet or the reverse. And so the same people acted as their own controls. And what we didn't tell them was that we would be measuring their leftovers so that we could figure out exactly, we knew exactly what we presented to these people, and we could measure every morsel of food that they ate over the course of each two-week period to figure out whether or not they were eating more or less calories on the ultra processed diet or the minimally processed diet despite being matched for the presented calories and many of these nutrients of concern. And we measured a variety of things during this process, including how much body fat changed and things like that. But the really striking result was that despite people not reporting any differences in fullness or appetite or desire to eat and not reporting any differences in the pleasantness of the meals, they ended up eating on average about 500 calories per day more during the ultra processed food environment exposure than they did during the minimally processed food environment exposure. They were spontaneously gaining weight and gaining fat when they were on the ultra processed diet and spontaneously losing weight and losing fat on the minimally processed diet. This is despite telling them not to be trying to gain or lose weight on the diet. In fact, they were blinded to their weight measurements. They were wearing loose fitting clothing so they couldn't tell if it was getting tighter or looser over the course of the experiment.