A new study suggests that children who consume more ultra-processed foods may show stronger reward-related brain responses to food cues, a pattern that researchers say could help explain later increases in body fat and waist circumference.
The findings, published in JAMA Network Open and reported by News Medical on October 23, 2026, come from the long-running BrainChild study at the Keck School of Medicine of USC. The research followed 46 children aged seven to 10 who began the study at a healthy weight, allowing scientists to examine early risk factors rather than the effects of existing obesity.
Brain scans pointed to stronger reward signals in children eating more UPFs
At the start of the study, researchers collected MRI scans while children viewed highly appetizing foods, along with dietary data and measurements of body mass index, body fat percentage and waist circumference. One year later, those measures were repeated. Children who ate more ultra-processed foods showed stronger responses in the dorsal striatum, a brain region involved in reward and motivation, when they looked at food images.
Those stronger responses were also associated with higher BMI and body fat percentage one year later. Overall, children who consumed more ultra-processed foods had greater waist circumference, BMI and body fat percentage at the end of the study. When researchers accounted for differences in dorsal striatum responses, the links with BMI and body fat percentage weakened, suggesting the brain response may help explain part of the association.
Why the food environment matters
Researchers emphasized that the burden should not fall only on families, noting that ultra-processed foods are often the most accessible, affordable and convenient options. The study was observational, so it cannot prove that ultra-processed foods caused the brain changes or the weight gain, but it adds to a growing body of evidence linking these products to health risks. A separate pooled analysis published in Family Medicine and Community Health found higher ultra-processed food intake was associated with increased risks of several chronic conditions, including obesity, metabolic syndrome and digestive disease.
The USC team said it plans to test the question further with an intervention study that would give children who regularly eat ultra-processed foods more minimally processed options and track whether their brain responses and body composition change over time. The researchers also said the BrainChild study will continue following participants through puberty and into young adulthood to document how diet, brain development and health evolve together.
For now, the study adds a new angle to an already heated nutrition debate: ultra-processed foods may affect more than calorie intake alone. They may also shape how the brain responds to food, potentially influencing eating behavior and body composition during a sensitive stage of development.
Photo source: AI-generated or edited image
