Matched-Calorie Meals Show Processing Level Alters Insulin, Energy Expenditure and Reward Brain Signals

Virginia Tech researchers used a sealed metabolic chamber and fMRI to compare responses within the same participants. After overnight fasts, subjects consumed either a NOVA-class 4 meal (PB&J bite, deli turkey, veggie chips, cookie, instant potatoes) or a NOVA-class 1 meal (banana, cranberries, cheese, egg). Postprandial insulin AUC rose higher after the ultraprocessed meal; carbohydrate oxidation fell and total energy expenditure increased, indicating a shift toward fat oxidation. Nucleus accumbens BOLD signals also diverged, consistent with altered reward processing.

These acute physiologic differences align with larger patterns from Hall et al. (Cell Metabolism 2019), where ad-libitum ultraprocessed diets drove +500 kcal/day intake and 0.9 kg weight gain over two weeks despite matched macros. The present data suggest mechanisms beyond energy density or palatability—possibly altered matrix structure, additives, or rapid absorption kinetics—that may promote compensatory overeating over repeated exposures.

The 57-participant cohort was young and healthy; effects in older or metabolically impaired groups remain unknown. Next steps require replication in free-living settings with continuous glucose monitoring and longer-term body-composition endpoints to test whether repeated exposure widens the observed insulin and oxidation gaps.