Children who eat more ultra-processed food show a stronger brain reward response to pictures of food — and tend to gain more body fat over time — according to a year-long study from the Keck School of Medicine at the University of Southern California, published in JAMA Network Open.
The study followed 46 children ages 7 to 10 who are part of USC's long-running BrainChild project on diabetes and obesity risk. All the children started the study at a healthy weight. Researchers tracked how much ultra-processed food — packaged snacks, sugary drinks, frozen meals — each child typically ate, then used brain imaging to measure activity in the dorsal striatum, a region tied to reward and craving, while the children viewed pictures of food.
A measurable, modest link
Kids who ate more ultra-processed food showed a stronger dorsal striatum response to images of high-calorie foods such as cookies and fries. That heightened brain response, the researchers found, statistically accounted for about 31% of the relationship between ultra-processed food intake and a child's body-mass index a year later, and 44% of the relationship with body fat percentage, according to coverage of the findings in Neuroscience News.
The researchers are careful about what the numbers do and don't show. The study is observational, meaning it can show an association but can't prove that ultra-processed food causes the brain changes or the weight gain — a child's biology could just as easily be shaping their eating habits as the other way around. The team also found that once they adjusted for how much added sugar a child consumed, the statistical link between ultra-processed food and the brain response weakened to the point of no longer being significant on its own, underscoring how tangled sugar, processing and brain reward circuits are in this age group, per a summary of the paper.
The lead researcher, USC's Kathleen Page, said the findings fit a broader pattern in pediatric nutrition research: highly processed foods are engineered to be easy to overeat, and children's still-developing brains may be especially sensitive to that pull. Page's team is now planning a follow-up trial that would swap a group of children's usual ultra-processed diets for minimally processed meals, to see whether the brain response — and the weight trajectory that goes with it — can be changed.
With fewer than 50 children in the study and no causal proof established, the findings aren't grounds for alarm on their own. But paired with decades of research linking processed-food-heavy diets to childhood obesity, researchers say they add a plausible biological mechanism — a brain tuned to crave more — to a problem long described mainly in terms of calories and access.
