Dorsal Striatum Activation Mediates 31% of Ultra-Processed Food Link to BMI Rise in 46 Children

The JAMA Network Open study combined baseline dietary recalls, body-composition measures, and task-based fMRI while participants viewed images of cookies and fries. Children consuming the most ultra-processed foods showed elevated reward-circuit activity; this neural signal prospectively tracked greater gains in BMI, percent body fat, and waist circumference twelve months later. When dorsal-striatum response was entered into the regression, the direct diet-to-BMI pathway weakened by nearly one-third, consistent with a partial mediation model.

Prior observational work has tied ultra-processed diets to obesity and cardiometabolic risk, yet mechanisms remained unclear. The present design isolates an early, pre-obesity neural marker in a narrow developmental window when reward circuitry is still plastic. This finding converges with adult cue-reactivity studies and with marketing data showing that ultra-processed products are engineered for maximal hedonic impact, suggesting the brain response may be both cause and consequence of repeated exposure.

Policy implications follow directly: school-meal standards and marketing restrictions targeting children could blunt cue sensitization before habits consolidate. A next logical step is a randomized controlled feeding trial that swaps ultra-processed items for minimally processed alternatives while repeating fMRI at six and twelve months to test whether striatal reactivity is modifiable and whether changes precede measurable weight divergence.