What actually makes ultraprocessed foods unhealthy?
NEWS | 22 October 2026
For breakfast, instant oatmeal. For lunch, a turkey sandwich on whole wheat bread. For dinner, a pasta bake with mozzarella cheese, and for dessert, low-fat yogurt and dried fruits. This diet is quite healthy and meets federal dietary guidelines—yet almost all of the calories come from ultraprocessed foods. In countries such as the U.S. and the U.K., ultraprocessed foods make up at least half of the average diet. Research from the past few years has linked eating a lot of them to heart disease, diabetes and early death. Those findings have put the foods on everyone’s radar—including federal policymakers in the U.S., who put out new dietary guidelines this year telling the public to avoid highly processed foods. The idea is that the processing itself might have effects on the food that make it easier for us to eat much more of it without noticing and for our body to digest it quickly or even that certain added ingredients such as preservatives and emulsifiers might be affecting our gut and how we handle blood glucose levels. But is the problem really the processing, or could it be the kinds of nutrients these highly processed foods tend to contain? Ultraprocessed foods are often laden with ingredients we’re told to avoid, and new findings are adding to the evidence that it’s the nutrient profile—such as low fiber content and high amounts of sugar and saturated fat—more than the processing that affects our health in the long run. This could explain the existence of “healthy” ultraprocessed foods, such as yogurt and whole-grain breads, and suggests that classifying foods based on processing is trickier than it seems because it could steer people away from foods that are possibly doing them no harm. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. To find out whether all ultraprocessed foods are equally bad for us, a team at the National Institutes of Health looked at national dietary survey data from more than 5,000 people. The researchers identified foods already labeled as “ultraprocessed,” according to a common food-classification system called Nova, and they checked whether they were also high in the things dietary guidelines tell us to cut back on: added sugar, salt, saturated fat, refined grains and alcohol. Unsurprisingly, about 90 percent of the calories that people consumed from ultraprocessed foods came from items that were high in nutrients to avoid. The researchers linked these same foods to higher body mass index and body fat, elevated insulin levels and increased inflammation. But notably, the ultraprocessed foods that contained fewer nutrients to avoid, such as canned beans and vegetables, low-sugar yogurt, diet sodas and low-fat products, weren’t correlated with the same adverse health indicators. This result suggests that the health effects linked to ultraprocessed foods might derive from their nutrition profile—although the observational nature of the data makes it difficult to identify what’s really behind the effects. The preliminary findings were presented at the American Society for Nutrition’s July meeting. Leah Lipsky, the study’s lead author and a nutrition epidemiologist at the NIH, says the research doesn’t mean people should eat a diet composed of only ultraprocessed foods with a better nutritional profile. “That’s not quite what we’re trying to get at,” she says. Instead it suggests that the “ultraprocessed” framing isn’t the best place to begin to understand a food’s health effects. Lipsky also notes that some food manufacturers are reformulating ultraprocessed foods to market them as more healthful choices. But this approach misses the point, she says. “We really want to try to encourage people to eat more foods straight from the produce section” rather than relying on the “ultraprocessed versus nonultraprocessed” distinction. Other large studies have also found that the link between ultraprocessed foods and disease risk is being driven by specific types of foods within the category. In particular, processed meats and cheese, as well as sweetened drinks, pose more of a risk, whereas foods such as breads, cereals and plant-based alternatives don’t have the same associations with poor health. In 2023 a team at the U.S. Department of Agriculture built a menu that met federal dietary guidelines even though almost all of the calories came from ultraprocessed foods, adding weight to the idea that not all these foods are necessarily “bad.” Yet some evidence suggests the processing still matters. In 2019 another team at the NIH reported on 20 adults who ate ultraprocessed and unprocessed diets with food options carefully matched for calories, sugar, fat, salt and fiber. On the ultraprocessed diet, people ate roughly 500 extra calories a day and gained weight. In a similar study reported last year, researchers in England gave 50 people two different diets, both designed to meet the U.K. healthy-eating guidance but with one consisting of ultraprocessed foods and the other of minimally processed ones. Both caused weight loss, but people lost twice as many pounds on average on the minimally processed diet. These studies, though short in duration, all point in the same direction, says Marion Nestle, professor emerita of nutrition at New York University: people have better health outcomes when they eat less ultraprocessed diets. Ultraprocessing physically alters the structure of some food molecules, she explains. Corn chips, for example, start as whole corn kernels, which get cooked in an alkaline solution to loosen the hull and ground into wet dough that is then formed into shapes and fried. This process eliminates the physical structure of the corn and creates something resembling a predigested food—which the gut digests faster than it would a whole food, Nestle says. Whether it is how soft and easy to chew these foods are or their tasty combinations of fat, salt and sugar, “something about [ultraprocessed foods] encourages people to eat more without realizing it,” Nestle says. The processing and the nutrient makeup may both matter. David Julian McClements, a food scientist at the University of Massachusetts Amherst, says the foods that end up in the ultraprocessed group tend to be the ones nutritionists have been warning about for decades anyway—those that have been broadly but imprecisely referred to as “junk food.” He thinks the processing does have real effects, but they’re “much smaller than the [nutritional]-composition effects.” The experts don’t think it’s realistic for most people to stop consuming ultraprocessed foods altogether. “Most people haven’t got the time, the energy, the money or the inclination” to cook from scratch, McClements says. His suggestion is for scientists to work out which processed foods cause harm and why, redesign those specifically and then test whether the redesign actually helps—although such trials are slow and expensive. Nestle’s advice to us is simpler. “Eating less junk food is good health advice,” she says.
Author: Allison Parshall. Lori Youmshajekian.
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