Hardly a day goes by without one or more studies or news stories about ultraprocessed foods (UPFs), most of them negative. The studies often demonize UPFs and urge the public to cut back on them or avoid them entirely. Emerging research suggests a more nuanced approach may be needed.
Many researchers warn that UPFs are associated with a higher risk for adverse health outcomes and may even contribute to premature death; however, the “healthiness” (often undefined in studies) of such foods is not always clearcut. Some studies, as well as a recent advisory from the American Heart Association (AHA), advise cutting back on UPFs with high fat, sugar, and salt content but also acknowledge that certain UPFs can be healthy, are often affordable, and could be part of a high-quality diet.
These developments seem to indicate that not all UPFs are the same and that the effect on weight gain and health may be tied to the nutritional value of the food and not just its level of processing.
The UPF category is “so broad it borders on useless,” wrote Nicola Guess, PhD, a registered dietitian at the University of Oxford in Oxford, England, in a recent essay. “It lumps store-bought whole-grain bread and hummus in with cookies, potato chips, and soda,” she added.
Are UPFs an Obesity Culprit?
There is general agreement that diets consisting primarily of UPFs are associated with increased energy intake and weight gain, but some experts question whether all UPFs cause people to put on weight.
“Epidemiological and experimental evidence consistently links UPF dietary patterns to increased energy intake, weight gain, and indicators of excess weight,” Filippa Juul of SUNY Downstate Health Sciences University, Brooklyn, New York, and the University of Sao Paulo, Sao Paulo, Brazil, and colleagues wrote in a recent Nature Reviews Endocrinology article. UPFs’ negative effects may arise from their “evolutionarily novel nutritional, physical, and chemical characteristics,” which could influence multiple biological pathways, including food reward systems, appetite and/or satiety regulation, and the microbiome, they added.
“To stem the global rise in obesity, multipronged policy efforts are needed to reduce UPF consumption and create health-promoting food systems,” the researchers concluded.
A 2024 evidence review concluded that greater UPF consumption has been a key driver of obesity and that the “obesogenic environment” must be changed to support efforts to reduce UPF intake. The lead author of that review, Samuel Dicken, PhD, of the Centre for Obesity Research, University College London, London, England, was also the lead author of a recent randomized controlled trial pitting a UPF diet against a minimally processed food (MPF) diet in an 8-week crossover trial. Food in both diets was provided to participants and was nutritionally matched in accordance with the UK’s official government advice on how to eat a healthy, balanced diet.
The MPF diet was more effective for weight loss than the UPF diet, yielding a 2% average reduction in weight compared with 1% for the UPF diet. Self-reported craving control was also significantly improved with the MPF diet, which may have helped support the lower calorie consumption, the authors suggested.
“Though a 2% reduction may not seem very big, that is only over eight weeks and without people trying to actively reduce their intake,” Dicken said at the time. “If we scaled these results up over the course of a year, we’d expect to see a 13% weight reduction in men and a 9% reduction in women on the minimally processed diet, but only a 4% weight reduction in men and 5% in women after the ultraprocessed diet. Over time this would start to become a big difference.”
However, in comments on the study for the UK’s Science Media Centre, several experts pointed out that regardless of the difference in diet, both groups lost weight, calling into question the idea that all UPFs cause weight gain.
“The study suggests that a diet meeting current dietary recommendations is not detrimental to weight maintenance, whether it is ultraprocessed or not,” Gunter Kuhnle, professor of nutrition and food science, University of Reading, Reading, England, noted in his response.
In addition, experts noted, the crossover design of the trial, which had both groups following both diets, with a washout period in between, led to an “order effect,” in which weight loss was less on the second diet across both trial arms.
In his response, Kevin McConway, PhD, emeritus professor of applied statistics, The Open University, Milton Keynes, England, took issue with the researchers’ methodology for extrapolating the diets’ effect over the course of a year and questioned whether the MPF diet would lead to greater weight loss over time.
Are All UPFs Unhealthy?
If UPFs’ effects on weight loss may depend on the foods’ quality, could the same be true about the health impacts?
Researchers often rely on definitions in the NOVA classification system, which groups foods into four categories ranging from unprocessed/minimally processed to ultraprocessed, in studies evaluating the health effects of UPFs. NOVA warns that the processes and ingredients used to manufacture UPFs typically make them nutritionally unbalanced and liable to be over-consumed and to replace foods that involve less processing.
Dietary guidelines, by contrast, focus less on how food is processed and instead emphasize nutritional content, caloric intake, and avoidance of too much added sugar, saturated fat, and salt. Certain foods may be considered healthy by government nutritional standards but not so by NOVA, and vice versa.
A recent large study of data from more than 200,000 US adults found that, after adjustment, participants who consumed the most UPFs, as defined by NOVA, were 11% more likely to develop cardiovascular disease (CVD) and 16% more likely to develop coronary heart disease (CHD) during the study period compared with those who consumed the least UPFs.
After researchers combined the results with those from 19 other studies, they found that participants who consumed the most UPFs were 17% more likely to develop CVD, 23% more likely to develop CHD, and 9% more likely to have a stroke compared with those who consumed fewest UPFs.
But that wasn’t the whole story. “Of note, divergent associations were observed for specific UPF groups in our cohorts,” the authors wrote. “Sugar-sweetened beverages, processed meats, and artificially sweetened beverages were associated with higher [cardiovascular disease] and [coronary heart disease] risk. Conversely, ultraprocessed savory snacks, cold cereals, and yogurt/dairy-based desserts were inversely associated with CVD and CHD risk. Ultra-processed bread and cold cereals were associated with lower stroke risk, and hard liquors with lower CHD risk.”
Similarly, a large study of data from the Nurses’ Health Study found that “high-quality meta-evidence shows that total UPF consumption is associated with higher T2D [type 2 diabetes] risk.” However, the authors wrote, among subgroups of UPFs, “cereals; dark and whole-grain breads; packaged sweet and savory snacks; fruit-based products; and yogurt and dairy-based desserts were associated with lower T2D risk.”
Moreover, in a proof-of-concept study, researchers developed a sample menu that included ≥80% calories from UPFs, as defined by NOVA, yet followed the recommendations for a healthy dietary pattern outlined in the 2020 Dietary Guidelines for Americans. A total of 91% of the calories ended up coming from UPFs, but the menu still scored 86 out of a possible 100 points on the 2015 Healthy Eating Index.
“This sample menu did not achieve a perfect score due primarily to excess sodium and an insufficient amount of whole grains,” the authors wrote. “This menu provided adequate amounts of all macro- and micro-nutrients, except vitamin D, vitamin E, and choline.”
A narrative review poses a key question: Just what might make UPFs bad? Is it the nutrient content or the processing that the food undergoes? The authors concluded that we don’t know — which is pretty much the case today. The AHA’s scientific advisory and many recent studies call for more research on the health impacts of food additives and processing techniques, as well as research to clarify the impact of UPFs that have better nutrition profiles.
In her recent essay, Guess called the focus on UPFs “a distraction from what we already know about nutrition.…We consume too much fast food, too many sugary beverages, too many cakes, doughnuts and chips. And we consume too few legumes, fruits and vegetables. We need better food and nutrition policies that make it easier for people to purchase and consume a healthier diet.”
Dicken reported being funded by the National Institute for Health and Care Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Center, a partnership between the UK NIHR and the UCLH National Health Service Foundation Trust; the Rosetrees Trust; and a UK Medical Research Council grant. Dicken reported receiving royalties from Amazon for a self-published book that mentions UPF, payments from Red Pen Reviews as a contributor, consultancy work for Consensus and Androlabs, and travel fees from a USDA National Institute of Food and Agriculture grant to present a workshop on food processing classifications.
Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.
