Kids who ate more ultra-processed food had stronger reward-brain reactions to pictures of cookies and fries, and they gained more body fat a year later

Ultra-processed foods make up about 67% of the calories American children eat. Researchers at the Keck School of Medicine of USC wanted to know whether those foods change how a child’s brain reacts to food. They studied 46 children aged 7 to 10, all at a healthy weight, scanning their brains while they looked at pictures of tempting foods like cookies and French fries. A year later, the team measured the children’s body fat and BMI again.

Children who ate more ultra-processed food showed stronger activity in the dorsal striatum, a part of the brain’s reward system, when they looked at the food pictures. And the children with the strongest reward response gained more body fat and had larger increases in BMI over the following year.

The brain response appeared to explain part of the link. When the researchers took the children’s dorsal striatum activity into account, the association between ultra-processed food intake and BMI gain shrank by 31%, and the association with body fat gain shrank by 44%.

“Children’s brains are still developing, habits are still forming and food preferences are still being made,” said senior author Kathleen Page, a professor of medicine and pediatrics at USC. “It’s an important period where the brain is very sensitive to food and the food environment.”

The idea that ultra-processed food drives overeating has strong support in adults. In a 2019 inpatient trial at the US National Institutes of Health, adults ate about 500 more calories a day on an ultra-processed diet than on an unprocessed one with the same nutrients available. What has been less clear is how this happens, especially in children.

This study offers a possible brain pathway: frequent ultra-processed food may tune the reward system to respond more strongly to tempting food, which in turn may encourage eating more. It fits with other recent work showing that ultra-processed meals can trigger a bigger insulin response and leave a distinct signature in the blood.

“This study goes beyond just understanding that UPFs affect weight gain,” Page said. “It actually gives us insight into the neurobiological underpinnings by which these foods may be linked to body composition over time.”

The second finding is about where solutions lie. Page stresses that the answer cannot rest on individual families alone, because ultra-processed foods are cheap, everywhere and easy to prepare. “Changing the food environment to help people access healthier, more minimally processed foods is an important part of the solution,” she said.

For parents, the practical takeaway is gradual: swapping some packaged snacks and cereals for minimally processed options, without making food a battle, may help a child’s taste and reward responses develop in a healthier direction. Page’s team is planning a trial to test exactly that.

There are limits to what this shows. With 46 children, the study was small, and it was observational, so it cannot show that ultra-processed food changes the brain or causes weight gain. Diet was self-reported, the follow-up lasted only a year, and all children came from one study in Southern California. The work was funded by the National Institutes of Health and the American Diabetes Association.

Source

Alves JM, Morgan E, Angelo B, et al. “Ultraprocessed Food Intake, Striatal Response to Food Cues, and Adiposity Gain in Children.” JAMA Network Open, 2026.
DOI: 10.1001/jamanetworkopen.2026.40252

Also cited

Hall KD, Ayuketah A, Brychta R, et al. “Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake.” Cell Metabolism, 2019.
DOI: 10.1016/j.cmet.2019.05.008