Ultraprocessed food alters metabolism and brain reward signals beyond its nutrient content

A study of healthy adults found that matched ultraprocessed meals produced stronger insulin and energy responses, reduced carbohydrate burning and were linked to activity in the brain’s reward system.

Researchers are adding to evidence that ultraprocessed foods may do more harm than simply loading meals with excess salt, sugar and fat. A study highlighted by McMaster University and reported in Nature Metabolism found that these products triggered stronger insulin and energy responses than meals with the same nutritional profile but less processing, suggesting that how food is made can shape the body’s reaction to it as much as what it contains.

In the experiment, 57 healthy-weight adults ate matched ultraprocessed and less processed meals. The Nature Metabolism study, published on 5 October 2026, found that ultraprocessed meals reduced carbohydrate oxidation, meaning the body burned less carbohydrate for energy after eating them. The researchers also reported a link between those metabolic changes and activity in the striatum, a brain region involved in processing food cues and reward. The authors said the findings point to effects beyond calories and macronutrients alone.

The work adds to a broader body of research that has repeatedly tied ultraprocessed foods to poorer health. In a 2025 analysis published by McMaster News, researchers said these foods were associated with higher risks of heart attack, stroke and other serious conditions. A separate McMaster report, backed by a 2025 EurekAlert release, said a landmark study linked heavier ultraprocessed food intake with higher blood pressure, insulin and triglyceride levels, all of which are recognised warning signs for cardiovascular disease and type 2 diabetes.

The latest findings are especially striking because they suggest biological effects may appear even in people without existing illness. According to the 2026 research briefing in Nature Metabolism, ultraprocessed foods may influence both metabolism and the brain’s handling of food value in ways that go beyond nutrient counts. That fits with the growing view among nutrition researchers that the level of processing itself may matter, not just the amount of fat, salt or sugar on the label.