Older adults can dramatically reduce the amount of ultraprocessed foods they eat while keeping a familiar, balanced diet – and this shift leads to improvements across several key markers related to how the body regulates appetite and metabolism. That’s the main finding of a new study my colleagues and I published in the journal Clinical Nutrition.
Ultraprocessed foods are made using industrial techniques and ingredients that aren’t typically used in home cooking. They often contain additives such as emulsifiers, flavorings, colors and preservatives. Common examples include packaged snacks, ready-to-eat meals and some processed meats. Studies have linked diets high in ultraprocessed foods to poorer health outcomes.
My team and I enrolled Americans ages 65 and older in our study, many of whom were overweight or had metabolic risk factors such as insulin resistance or high cholesterol. Participants followed two diets low in ultraprocessed foods for eight weeks each. One included lean red meat (pork); the other was vegetarian with milk and eggs. For two weeks in between, participants returned to their usual diets.
A total of 43 people began the dietary intervention, and 36 completed the full study.
In both diets, ultraprocessed foods made up less than 15% of the total calories – a significant reduction from the typical American diet, where more than 50% of total calories comes from ultraprocessed foods. The diets were designed to be realistic for everyday eating, and participants were not instructed to restrict calories, lose weight or change their physical activity.
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We prepared, portioned and provided all meals and snacks for the study. Both diets emphasized minimally processed ingredients and aligned with the 2020-2025 Dietary Guidelines for Americans, the U.S. government’s nutrient-based recommendations for healthy eating, while providing similar calories and amounts of key nutrients.
The 2025-2030 Dietary Guidelines for Americans, released on Jan. 7, 2026, explicitly recommend eating less ultraprocessed food, but the previous versions of the guidelines did not specifically address food processing. Our feeding study design allowed us, for the first time, to examine the health effects of reducing ultraprocessed foods while keeping nutrient levels consistent with recommended targets.
We compared how participants fared while eating their habitual diets with how they responded to the two diets that were low in ultraprocessed foods. During the periods when participants ate fewer ultraprocessed foods, they naturally consumed fewer calories and lost weight, including total and abdominal body fat. Beyond weight loss, they also showed meaningful improvements in insulin sensitivity, healthier cholesterol levels, fewer signs of inflammation and favorable changes in hormones that help regulate appetite and metabolism.
These improvements were similar whether participants followed the meat-based or the vegetarian diet.
Why it matters
Ultraprocessed foods make up more than half the calories consumed by most U.S. adults. Although these foods are convenient and widely available, studies that track people’s diets over time increasingly link them with obesity and age-related chronic diseases such as Type 2 diabetes and heart disease. With older adults making up a growing share of the global population, strategies that preserve metabolic health could support healthy aging.
Most previous feeding studies testing how ultraprocessed foods affect people’s health haven’t reflected real-world eating, especially among Americans. For example, some studies have compared diets made up almost entirely of ultraprocessed foods with diets that contain little to none at all.
Our study aimed to more closely approximate people’s experience while still closely tracking the foods they consumed. It is the first to show that for older adults a realistic reduction in ultraprocessed foods, outside the lab, has measurable health benefits beyond just losing weight. For older adults especially, maintaining metabolic health helps preserve mobility, independence and quality of life.
What’s still unknown
Our study was small, reflecting the complexity of studies in which researchers tightly control what participants eat. It was not designed to show whether the metabolic improvements we observed can prevent or delay diseases such as diabetes or heart disease over time. Larger, longer studies will be needed to answer that.
On the practical side, it’s still unclear whether people can cut back on ultraprocessed foods in their daily lives without structured support, and what strategies would make it easier to do so. It’s also not fully understood which aspects of processing – for example, additives, emulsifiers or extrusion – matter more for health.
Answering these questions could help manufacturers produce foods that are healthier but still convenient – and make it easier for people to choose healthier food options.
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