Every parent knows the pull of a snack aisle, but a new brain-imaging study suggests the effect of ultra-processed foods and kids may start in the reward system itself. Researchers at the Keck School of Medicine of USC found that children who ate more ultra-processed foods (UPFs) showed a stronger brain response to pictures of tempting foods, and that response was linked to bigger gains in body fat a year later.
Ultra-Processed Foods and Kids: What the Study Did
The paper, published in JAMA Network Open (2026; 9(10):e2640252), is titled “Ultraprocessed Food Intake, Striatal Response to Food Cues, and Adiposity Gain in Children.” It followed 46 children aged 7 to 10 enrolled in the ongoing BrainChild study. All were at a healthy weight when the study began.
At the start, the children had MRI brain scans while viewing pictures of appealing foods such as cookies or French fries. The team assessed their diets and measured BMI, body fat percentage and waist circumference, then measured again after one year. The senior author was Kathleen A. Page, MD, co-chief of the Division of Endocrinology and Diabetes at Keck.
What Happened in the Brain
Children who ate more UPFs showed greater activity in the dorsal striatum, a brain region that helps regulate reward and motivation, when they looked at the food pictures. In turn, children with stronger dorsal striatum responses tended to have bigger increases in BMI and body fat percentage over the following year.
By the end of the study, higher UPF intake was generally linked to higher BMI, higher body fat percentage and larger waist circumference.
The Numbers Behind the Link
When the researchers adjusted for the dorsal striatum response, the relationship between UPF intake and BMI was 31% weaker, and the relationship with body fat percentage dropped by 44%. That suggests the brain response may explain part of the connection, though not all of it. The coverage also cites a figure that UPFs make up about 67% of the calories US children consume, but gives no source for it, so treat that number with care.
Why Researchers Focus on Childhood
Dr. Page said, “Children’s brains are still developing, habits are still forming and food preferences are still being made.” That is why researchers are interested in this age group: preferences set in childhood can last.
What This Study Cannot Prove
This was an observational study with only 46 children, so it cannot show that UPFs directly cause changes in brain activity or weight gain. The authors say the results do not demonstrate that these foods directly alter brain function. They describe the work as offering a possible biological explanation for an association seen in earlier research. The researchers plan an intervention study in which children who regularly eat UPFs are given more minimally processed alternatives, and they will keep following the BrainChild participants through puberty and into early adulthood.
Realistic Tips for Parents
Page noted that improving diets “cannot depend entirely on individual families,” because UPFs are often cheap, widely available and easy to prepare. Within that reality, small swaps can still help:
- Start with one swap. Replace one packaged snack a day with fruit, nuts or yogurt.
- Read the ingredient list. Long lists with unfamiliar additives often signal heavy processing.
- Cook simple. Eggs, beans, rice and frozen vegetables are fast and low-cost.
- Do not label foods “bad.” Calm, consistent habits work better than strict rules.
- Talk to your pediatrician. If you are worried about your child’s weight, ask for personal guidance.
The Bottom Line
In a small observational study, kids who ate more ultra-processed foods showed a stronger brain reward response to food cues, which was tied to more body fat gain over a year. It is an early clue, not proof. For more family health reading, see our age-by-age vaccine guide for kids and our report on gut health research. The paper is available through its JAMA Network Open DOI link.
This article is for general information and is not medical advice. Always follow your child’s pediatrician’s guidance.
