Kids Who Eat More Ultraprocessed Foods Show Stronger Brain Cravings and Gain More Body Fat, USC Study Finds

LOS ANGELES — Children who eat more ultraprocessed foods show stronger activity in the brain's reward system when they see pictures of tempting foods such as cookies and french fries, a new study has found. That heightened brain response was linked to gains in body fat a year later.

Researchers at the Keck School of Medicine of the University of Southern California published the findings in the journal JAMA Network Open. They say the results suggest the brain may become more sensitive to food cues in children who eat more of these products. That sensitivity may help explain why ultraprocessed foods have been tied to weight gain.

"Children's brains are still developing, habits are still forming and food preferences are still being made," said Dr. Kathleen A. Page, the study's senior author, a professor of medicine and pediatrics and co-chief of the Division of Endocrinology and Diabetes at Keck. "It's an important period where the brain is very sensitive to food and the food environment."

A large part of children's diets

Ultraprocessed foods are manufactured products such as breakfast cereals, packaged breads and instant soups. They are designed to be tasty, convenient and long-lasting on store shelves, and they often contain artificial sweeteners, colorings and other ingredients that people do not typically use when cooking at home.

They make up a large share of what American children eat. On average, U.S. children get about 67% of their daily calories from ultraprocessed foods, according to the researchers.

Earlier studies have linked these foods to weight gain, type 2 diabetes and heart disease. Scientists have known less about how the brain might play a role. The USC team set out to help close that gap by combining brain scans with diet data and measurements of body composition.

"We're particularly interested in understanding these processes in children, because we believe that intervening early could make a real difference," Page said.

Inside the study

The research involved 46 children, ages 7 to 10, enrolled in BrainChild, a long-term study of diabetes and obesity risk. All of the children were at a healthy weight when the study began. That allowed the researchers to look at early signs of risk before weight problems developed.

At the start, each child underwent a magnetic resonance imaging, or MRI, scan while viewing photos of highly appealing foods. Researchers also collected information about each child's diet and measured body mass index, body fat percentage and waist size.

One year later, they measured those three body indicators again.

What the brain scans showed

Children who ate more ultraprocessed foods had stronger responses to the food images in the dorsal striatum, a part of the brain involved in reward and motivation. The region helps drive the desire to seek out things that feel rewarding, including food.

Stronger activity in that region was in turn linked to larger increases in body mass index and body fat percentage over the following year.

Overall, children who ate more ultraprocessed foods ended the study with larger waistlines, higher BMIs and higher body fat percentages.

The researchers then accounted for differences in how each child's dorsal striatum responded to food images. When they did, the link between ultraprocessed food intake and BMI weakened by 31%, and the link with body fat percentage weakened by 44%.

That means differences in brain responses may explain a meaningful part of the connection between eating ultraprocessed foods and gaining weight.

"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."

Limits of the findings

The researchers stress that the study was observational. It shows an association between diet, brain activity and weight gain, but it cannot prove that ultraprocessed foods cause the brain changes or the added body fat.

The study was also relatively small, with fewer than 50 children, and followed them for one year. Larger and longer studies would be needed to confirm the pattern.

To test cause and effect, Page plans an intervention study. Children who regularly eat ultraprocessed foods would be given more minimally processed foods instead. Researchers would then track whether their brain responses to food images change over time and whether those changes are tied to less weight gain.

Not just a family problem

The researchers say responsibility should not fall only on parents and children to change their diets. Ultraprocessed foods are often the most available, affordable and convenient options, especially for busy or lower-income households.

"Changing the food environment to help people access healthier, more minimally processed foods is an important part of the solution," Page said.

The findings add to a growing debate over the role of ultraprocessed foods in childhood obesity. Health advocates and policymakers have increasingly focused on these products, from school meal standards to food labeling and advertising aimed at children.

What comes next

The BrainChild study will continue to follow its participants through puberty and into young adulthood. Researchers will track changes in their brains and bodies along with the links between diet and overall health.

For now, the research offers a new look at how what children eat may connect to how their brains respond to food. That window into early childhood could help shape efforts to prevent obesity before it starts.

The study, titled "Ultraprocessed Food Intake, Striatal Response to Food Cues, and Adiposity Gain in Children," was published in JAMA Network Open.