Jessica Wilson is passionate about the pupusas from Costco. Not just because they’re tasty, but also because they’ve helped the California-based registered dietitian fight back against the mounting war on ultra-processed foods.
It all started in the summer of 2023, when author and infectious-disease physician Dr. Chris van Tulleken was promoting his book, Ultra-Processed People. While writing it, van Tulleken spent a month eating mostly foods like chips, soda, bagged bread, frozen food, and cereal. “What happened to me is exactly what the research says would happen to everyone,” van Tulleken says: he felt worse, he gained weight, his hormone levels went crazy, and before-and-after MRI scans showed signs of changes in his brain. As van Tulleken saw it, the experiment highlighted the “terrible emergency” of society’s love affair with ultra-processed foods.
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Wilson, who specializes in working with clients from marginalized groups, was irked. She felt that van Tulleken’s experiment was over-sensationalized and that the news coverage of it shamed people who regularly eat processed foods—in other words, the vast majority of Americans, particularly the millions who are food insecure or have limited access to fresh food; they also tend to be lower income and people of color. Wilson felt the buzz ignored this “food apartheid,” as well as the massive diversity of foods that can be considered ultra-processed: a category that includes everything from vegan meat replacements and nondairy milks to potato chips and candy. “How can this entire category of foods be something we’re supposed to avoid?” Wilson wondered.
So she did her own experiment. Like van Tulleken, Wilson for a month got 80% of her daily calories from highly processed foods, not much more than the average American. She swapped her morning eggs for soy chorizo and replaced her thrown-together lunches—sometimes as simple as beans with avocado and hot sauce—with Trader Joe’s ready-to-eat tamales. She snacked on cashew-milk yogurt with jam. For dinner she’d have one of her beloved Costco pupusas, or maybe chicken sausage with veggies and Tater-Tots. She wasn’t subsisting on Fritos, but these were also decidedly not whole foods.
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A weird thing happened. Wilson found that she had more energy and less anxiety. She didn’t need as much coffee to get through the day and felt more motivated. She felt better eating an ultra-processed diet than she had before, a change she attributes to taking in more calories by eating full meals, instead of haphazard combinations of whole-food ingredients.
How could two people eating the same type of foods have such different experiences? And could it be true that not all ultra-processed foods deserve their bad reputation?
These hotly debated questions come at a crucial moment. In 2025, the U.S. government will release an updated version of the Dietary Guidelines for Americans, which tell people what they should eat and policymakers how to shape things like school lunches and SNAP education programs. The new edition may include, for the first time, guidance on ultra-processed foods. Officials at the U.S. Food and Drug Administration are also reportedly weighing new regulatory approaches for these products.
The food industry, predictably, maintains that ultra-processed foods have been unfairly demonized and can be part of a healthy diet. Likely sensing a threat to their bottom line, large food companies have reportedly already started lobbying against recommendations around processed-food consumption.
What’s more surprising is that even one dietitian would take their side, defending a group of foods that, according to 2024 research, has been linked to dozens of poor health outcomes ranging from depression and diabetes to cancer, cardiovascular disease, and cognitive impairment. Wilson has endured plenty of criticism for her position, which is not popular among the nutrition-science establishment. But she stands by it. Sweeping recommendations to avoid all ultra-processed foods stand to confuse people and make them feel bad about their diets, Wilson says—with questionable upside for their health.
What is aprocessed food, anyway? It’s a rather new concept. Foods are mainly judged by how many vitamins, minerals, and macronutrients (think fat, protein, and carbs) they contain, as well as their sugar, salt, and saturated-fat contents. There’s no level of processing on a food label.
Scientists don’t agree on exactly how to define processed foods. If you give two experts the same ingredient list, “they will have different opinions about whether something is processed or not,” says Giulia Menichetti, a principal investigator at Harvard Medical School who researches food chemistry. Take milk. Some experts consider it a processed food because it goes through pasteurization to kill pathogens. Others don’t think it belongs in that category because plain milk typically contains few additives beyond vitamins.
The most widely used food-classification system, known as NOVA, uses the latter interpretation. It defines an unprocessed food as one that comes directly from a plant or animal, like a fresh-picked apple. A minimally processed food may have undergone a procedure like cleaning, freezing, or drying, but hasn’t been much altered from its original form. Examples include eggs, whole grains, some frozen produce, and milk.
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Under NOVA, a processed food contains added ingredients to make it taste better or last longer, such as many canned products, cured meats, and cheeses. An ultra-processed food, meanwhile, is made largely or entirely from oils, sugars, starches, and ingredients you wouldn’t buy yourself at the grocery store—things like hydrogenated fats, emulsifiers, flavor enhancers, and other additives. Everything from packaged cookies to flavored yogurt to baby formula fits that description.
“You end up with a system where gummy bears and canned kidney beans” aren’t treated so differently, says Julie Hess, a research nutritionist with the USDA. At the end of the day, they’re both processed.
Why should that matter to anyone aside from researchers and dietitians? Because most people who care about their health have the same question about processed foods: Are they killing me? And right now—despite their looming possible inclusion in dietary guidelines—no one really knows the answer. There’s limited cause-and-effect research on how processed foods affect health, and scientists and policymakers have yet to come up with a good way to, as Hess says, “meaningfully delineate between nutrient-dense foods and nutrient-poor options”—to separate the kidney beans from the gummy bears.
Hess and her colleagues drove home that point in a 2023 study, for which they created a hypothetical diet almost entirely made up of ultra-processed foods like breakfast burritos, canned soup, and instant oatmeal. The diet wasn’t nutritionally stellar—it was high in sodium and low in whole grains—but scored an 86 out of 100 on a measure of adherence to the federal dietary guidelines, considerably better than the average American’s score of 59. The experiment highlighted that there are nutritious ultra-processed foods, and that certain ones “may make it easier and more convenient to have a healthy diet, because a lot of these foods are more shelf-stable, they’re more cost-effective, they’re sometimes easier to access,” Hess says.
A 2024 study backs up the idea that people who eat processed foods can still be healthy. Although the researchers did find links between heavily processed diets and risk of premature death, they concluded that overall diet quality may be more important than how many processed foods someone eats. In other words, if someone is eating plenty of nutritious foods, maybe it’s OK if some come from a wrapper. The study aimed to correct “the potential misperception that all ultra-processed food products should be universally restricted and to avoid oversimplification when formulating dietary recommendations,” the authors wrote.
Even vocal critics of ultra-processed foods, like van Tulleken, agree that not all are equal. He’s particularly concerned about those that are high in salt, sugar, or saturated fat, which is true of many ultra-processed foods but not all of them. These elements have long been nemeses of the nutrition world, but van Tulleken argues they’re especially damaging when eaten in industrially made foods spiked with additives and designed to be as appetizing as possible. “We’ve had fat, salt, and sugar in abundance in our diet for a century, and I’m the first to say they are the nutrients of concern,” van Tulleken says. “But they weren’t a concern when we were mixing them up at home, because when you cook at home, your purpose is not to get me to eat 3,000 calories in half an hour.”
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Industrial production means that ingredients undergo complex chemical changes, the implications of which researchers don’t fully understand, says Menichetti, the food chemist. “We co-evolved with our food, so if our bodies got used to certain chemicals in certain ranges,” altering foods’ compositions via processing could change the way they affect human health, she says.
Already, some studies suggest that ultra-processed foods affect the body differently than unprocessed ones, regardless of their nutrient profiles. One 2024 study found that plant-based foods, which are traditionally considered healthy, lose many of their benefits and even contribute to higher risks of heart disease and death when they’re ultra-processed (when a whole grain turns into store-bought bread, for example). And a 2020 review article found numerous bad outcomes—cancer, cardiovascular disease, IBS, depression, and more—linked to ultra-processed diets and not a single study connecting them to better health. Those results suggest that a food’s processing level is linked to its “healthiness,” the authors wrote.
A 2019 study from the National Institutes of Health (NIH) provides some of the strongest evidence that ultra-processed foods can directly cause health problems. For the study, 20 U.S. adults lived in an NIH laboratory for a month. For two weeks, they ate minimally processed foods like vegetables and nuts. For the other two, they ate ultra-processed foods like bagels and canned pasta.
The two diets were designed to be equivalent in calories, sugar, salt, and macronutrients, but people could eat as much or as little as they wanted at mealtimes. On the ultra-processed diet, people ate more and gained weight. Meanwhile, on the minimally processed one, they lost weight, had positive hormonal changes, and saw markers of inflammation drop. Those findings suggest something about ultra-processed foods drives people to overeat and may cause health problems, says lead author Kevin Hall—but it’s not yet clear what that something may be.
“There’s a very, very long list of potential candidates,” Hall says. Is it the combination of ingredients manufacturers use to make foods tasty? Is there a problematic ingredient or additive? Does something about the manufacturing process degrade the food’s quality? Or is the explanation something else entirely?
In November, the 2025 Dietary Guidelines Advisory Committee is expected to release a report on ultra-processed foods, which will assess the available data on how they affect the body. More research is needed. But at a meeting in May, committee member Dr. Fatima Cody Stanford, an obesity-medicine specialist at Massachusetts General Hospital, previewed the group’s findings: that people who eat highly processed diets are at risk of obesity.
Even with questions outstanding, we already know that some ultra-processed foods are harmful, says Kendra Chow, a registered dietitian and policy and public affairs manager at the nonprofit World Cancer Research Fund International. Stereotypical “junk foods” that are high in salt, sugar, or saturated fat—things like chips, candy, and hot dogs—have long been linked to health problems like cancer and heart disease. The science on those foods is clear enough that people should limit how often they eat them, she says.
What’s trickier, Chow says, is figuring out what to do about foods that are ultra-processed but seem to have more nutritional value, like flavored yogurts and store-bought vegetable pasta sauces. “Stigmatizing a broad category of foods that also includes lower-cost, accessible options, especially without providing an alternative or improving access and affordability of healthy foods,” is not the answer, she says.
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Despite his prominent campaign against ultra-processed foods, van Tulleken agrees. He realizes a ban on them wouldn’t be practical; it would essentially wipe out the modern food system, with particularly disastrous consequences for people of lower socio-economic status. (He would, however, like to see more regulation of food marketing and warning labels on processed products high in salt, sugar, or saturated fat.) Though he feels strongly that ultra-processed foods are contributing to a modern public-health crisis, van Tulleken also recognizes that they serve an imperfect purpose in a world where many people are strapped for time and money.
Even Hall, the NIH researcher, eats ultra-processed foods—and not infrequently. Most days for lunch, he heats up a frozen meal in the microwave. “I’ll try to choose one that is high in fiber and whole grains and legumes and low in sodium and saturated fat and sugar,” he says. But he knows that technically, it’s in the same category as a Twinkie.
After her experiment last summer, Wilson also continues to eat plenty of processed foods—and to feel good about it. To her, the debate is about more than food; it’s also about the realities of living in a country where grocery prices are spiking and lots of people simply don’t have the resources to eat three home-cooked meals made from fresh ingredients every single day.
“People often assume that a dietitian’s day is telling people to eat less,” Wilson says. But she says she spends far more time helping people figure out how to eat more—whether because they’re trying to feed a family on a tight budget or because they simply don’t have time and energy to cook—and how to add nutrient-rich foods to their diets in a way that’s affordable. For some of those people, ultra-processed foods may be the difference between going to bed hungry or full, Wilson says. She’d pick full every time.