Two Meals With Matching Nutrition Labels Triggered Different Reactions in the Body and Brain

Keypoints:

• 57 healthy-weight adults aged 18 to 45 took part in a randomized crossover study
• The two meals were matched within 1% for calories, carbohydrates, fat, protein, water and salt
• The ultraprocessed meal produced a higher insulin response and kept blood sugar elevated for longer
• Participants burned more total energy but oxidized less carbohydrate after the ultraprocessed meal
• The findings were published in Nature Metabolism on 5 October

Researchers at the Fralin Biomedical Research Institute at Virginia Tech Carilion (VTC) fed volunteers two 300-calorie meals that looked identical on paper. The meals matched within 1% of calories, carbohydrates, fat, protein, water and salt. The only difference was how much industrial processing each food had been through. First author Zach Hutelin said that if the meals had nutrition labels, they would be practically identical.

The team recruited 57 healthy adults, and 32 completed both the metabolic and brain-imaging sessions. Meals were sorted using the NOVA food classification system, which groups foods into four categories by level of industrial processing. The highly processed meal included a peanut butter and jelly sandwich, deli turkey, veggie chips, a cookie, breakfast cereal and instant mashed potatoes. The minimally processed meal was sliced banana, dried unsweetened cranberries, whole cheese and a hard-boiled egg.

Each volunteer ate within 10 minutes inside an airtight metabolic chamber, which tracks energy use in real time. Blood was drawn right after eating and six more times over the next three hours. Hutelin said every single metabolic measure differed between the two meals.

The ultraprocessed meal drove a much higher insulin response, and blood sugar stayed elevated a little longer. Participants spent more total energy processing it. They also oxidized significantly less carbohydrate for fuel than after the whole-food meal.

The brain scans added another layer. Volunteers viewed pictures of the matched foods while stating how much they would pay for each. Activity in the ventral striatum and nucleus accumbens, two hubs of the brain's reward system, shifted between the two meals. The size of each person's change in carbohydrate burning predicted that brain response. Stated willingness to pay did not differ, so the reward circuits registered the gap without participants noticing.

The result speaks to a long-running debate. Ultraprocessed foods supply more than half of daily calories in the United States, and diets heavy in them are linked to obesity, type 2 diabetes and heart disease. Scientists have argued over whether the harm comes from added sugar, fat and salt or from processing itself. Carlos Monteiro, the University of São Paulo professor who created the NOVA system, called the study a novel and important contribution because the brain ultimately steers eating behavior.

The authors are careful about limits. The study used a single 300-calorie meal in young, healthy people. Future work will test which parts of industrial formulation, such as additives or specific processing steps, drive the effect. The research was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and a National Science Foundation graduate research fellowship.

A nutrition label tells you what is in a meal. This study suggests it may not tell you how the body will handle it.