Sam Srisatta, a 20-year-old volunteer, is dedicating a month of his life to a groundbreaking research project that could reshape nutritional guidelines in the U.S. His participation is part of a study aimed at understanding the health effects of ultraprocessed foods, which account for nearly 70% of the country’s food supply.
Each day, Srisatta undergoes a rigorous routine at the National Institutes of Health Clinical Center in Bethesda, Maryland. Nurses track his vitals, including weight and bowel movements, while tests are conducted to observe how his body reacts to different foods. On some days, his blood is drawn to measure metabolic responses; on others, he lies in a bubble chamber to measure his calorie expenditure at rest. After these tests, Srisatta is given 15 minutes to eat his breakfast, after which it is carefully weighed and recorded. At lunch and dinner, he has an hour to eat before the remaining food is collected and measured, and his vitals are recorded again. The rest of the day is free for leisure activities such as reading, video games, exercise, or sleep.
This study, which involves 36 other participants, is exploring the health impact of ultraprocessed foods in a controlled clinical environment. Ultraprocessed foods, which are manufactured using refined ingredients and additives not typically found in home kitchens, are engineered to be highly palatable by combining sugar, salt, and fats to hit a “bliss point”—a taste so irresistible it encourages overeating.
The Risks of Ultraprocessed Foods
As food science has advanced, the ability to create artificial flavors and textures that home-cooked meals cannot replicate has grown, making ultraprocessed foods even more alluring. However, many studies have linked these foods to increased risks of obesity, chronic diseases like cancer and heart disease, type 2 diabetes, and even depression. Such diet-related conditions are responsible for at least half of all U.S. deaths, disproportionately affecting Black, Indigenous, and low-income communities, and contributing to $4.5 trillion in annual healthcare costs, according to U.S. Food and Drug Administration officials.
Yet, not all ultraprocessed foods may have the same impact on health, a question that has perplexed scientists and delayed regulatory action. Kevin Hall, a senior investigator with the National Institute of Diabetes and Digestive and Kidney Diseases, is leading this study to unravel how different types of ultraprocessed foods may contribute to poor health. “There’s a lot of debate about whether all ultraprocessed foods are bad for you,” Hall said. “If we can pinpoint what drives poor health, we can help the FDA and policymakers make informed decisions on food labeling and regulations.”
A Surprising Finding: Overeating Ultraprocessed Foods
In a previous study published in 2019, Hall’s team observed that healthy volunteers who consumed ultraprocessed foods like sugary cereals and muffins ended up eating an average of 500 extra calories a day compared to when they consumed minimally processed foods like Greek yogurt with fresh fruit and nuts. This was despite both diets having the same total calorie count. Interestingly, participants gained weight on the ultraprocessed diet and lost weight on the minimally processed one, leading researchers to question why ultraprocessed foods have such an effect on eating habits.
A similar study in Japan revealed an even greater increase in caloric intake—volunteers consuming ultraprocessed foods ate an additional 813 calories per day. “What we’re seeing is an overwhelming tendency to overeat when exposed to ultraprocessed foods,” said molecular biologist Marion Nestle, who praised Hall’s research for its controlled environment, which eliminated the possibility of self-reporting biases that often skew the results of diet studies.
The Global Epidemic of Obesity and the Role of Ultraprocessed Foods
Obesity is a global issue, and by 2035, more than half the world’s population is expected to be overweight or obese, according to the World Health Organization. In the U.S., nearly 260 million people are projected to be overweight or obese by 2050 unless significant action is taken. The role of ultraprocessed foods in this obesity epidemic is now being investigated as part of the U.S. 2025-2030 Dietary Guidelines, which will provide the foundation for federal nutrition policy for the next five years.
“Ultraprocessed foods may be the most important concept to come to nutrition since vitamins,” Nestle said. Hall’s research, which includes randomized controlled trials, is integral to the ongoing debate about how these foods affect our health.
The Need for More Research
A key issue in understanding the full impact of ultraprocessed foods is the lack of long-term, large-scale studies. The Dietary Guidelines Advisory Committee, tasked with reviewing the latest science on ultraprocessed foods, has only found limited evidence to link these foods to weight gain and obesity. Hall’s 2019 study, for example, was excluded from their analysis due to its smaller sample size and shorter duration.
Despite the exclusion of some studies, there is a growing consensus that ultraprocessed foods are contributing to the global obesity crisis. The difficulty lies in funding and conducting long-term, large-scale research due to the complexity of tracking dietary habits and the high costs associated with metabolic ward studies. “We already know these foods make people eat more than they realize,” Nestle said. “What else do we need to know before we make public health recommendations?”
As more research is conducted, experts agree that reducing the intake of ultraprocessed foods should be a priority for public health. The final 2025-2030 U.S. Dietary Guidelines may offer stronger recommendations on the issue, but for now, many advocates, including Nestle and Bonnie Liebman of the Center for Science in the Public Interest, agree that more research is essential to understand the full impact of ultraprocessed foods on health.
Until then, policymakers, nutritionists, and the public must continue to scrutinize the evidence and work toward solutions that can reduce the harm caused by these highly processed foods. “It’s really that simple: reduce intake of ultraprocessed foods,” Nestle concluded.
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