Ultra-processed foods heighten kids’ brain reward response

Children who ate more ultra-processed food showed stronger brain reactions to pictures of appetizing food. A recent study from the Keck School of Medicine at USC found the link. The team followed 46 children aged 7 to 10, all at a healthy weight when they started. At the start, the researchers used functional magnetic resonance imaging, or fMRI, to scan each child while they looked at pictures of foods such as French fries and cookies. Children who ate more ultra-processed foods, such as packaged cereals, chips and soda, had stronger blood-oxygen-level-dependent signals in a brain region called the dorsal striatum. That region is a key part of the dopamine-driven reward system, which helps shape habits and motivated actions.

The researchers say this stronger brain response accounted for a large part of the link between diet and weight. After one year, children with higher ultra-processed-food intake had greater waist circumference. Their BMI and body-fat percentage increases were positive, but not statistically firm. When the team accounted for activity in the dorsal striatum, the link weakened by 31 percent for BMI and by 44 percent for body fat. The authors describe the brain’s sensitivity to food cues as a possible biological pathway linking these diets to weight gain.

Reward signals explain weight gain

Because the children started at a healthy weight, the researchers could see that the brain changes appear before visible weight gain. The authors say this suggests early intervention could be effective. They plan randomized trials. In those trials, children who regularly eat ultra-processed foods would receive structured, minimally processed diets. The trials would test whether the brain’s reward responses can be lowered, and whether that reduces obesity risk over time.

Ultra-processed foods make up about 67% of the calories children in the United States eat each day. They are low in fiber and micronutrients, and high in refined carbs, saturated fats and additives. The authors warn that marketing, price and convenience make it hard for families to choose healthier options. They argue that the food environment needs to change to protect children’s developing brains and bodies.