Children who eat more ultra-processed foods (UPFs) show stronger responses in the brain's reward network when viewing images of appetizing foods—and these brain responses are linked to increases in body fat one year later. The findings, just published in JAMA Network Open , suggest that the brain may become more sensitive to food cues when children consume more UPFs.
UPFs are manufactured food products—such as breakfast cereals, packaged bread and instant soups—that are designed to be highly palatable, convenient and shelf-stable. They often contain artificial sweeteners, colors and other ingredients that people do not typically use when cooking at home. On average, U.S. children get about 67% of their daily calories from UPFs.
Past studies have linked these products to weight gain, type 2 diabetes and cardiovascular disease, but researchers do not yet know how the brain's reward network may contribute to these risks. The new study, funded in part by the National Institutes of Health, collected magnetic resonance imaging (MRI) brain scans, dietary information and data on children's body composition to help fill that gap.
"Children's brains are still developing, habits are still forming and food preferences are still being made. It's an important period where the brain is very sensitive to food and the food environment," said the study's senior author, Kathleen A. Page, MD , professor of medicine and pediatrics and co-chief of the Division of Endocrinology and Diabetes at the Keck School of Medicine of USC . "We're particularly interested in understanding these processes in children, because we believe that intervening early could make a real difference."
Linking UPFs to weight gain
The research included 46 children, ages seven to 10, who are part of the long-term BrainChild study of diabetes and obesity risk. All children started the study at a healthy weight, allowing researchers to focus on the early risks of UPFs.
At the beginning of the study, researchers collected MRI scans of each child while they viewed photos of highly appetizing foods (such as cookies or French fries). They also collected data on diet, body mass index (BMI), body fat percentage and waist circumference. One year later, they measured BMI, body fat percentage and waist circumference again.
Children who consumed more UPFs had stronger responses to food images in the dorsal striatum, a brain region involved in reward and motivation. Stronger responses in the dorsal striatum were also associated with increased BMI and body fat percentage one year later.
Overall, children who ate more UPFs had greater waist circumference, BMI and body fat percentage at the end of the study. But when researchers accounted for differences in children's dorsal striatum responses to food images, the associations with BMI and body fat percentage weakened by 31% and 44%, respectively. That suggests the differences in brain responses may help explain the link between UPF consumption and weight gain.
"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."
Improving the food environment
The researchers emphasize that the onus should not fall solely on families and children to make dietary changes, because UPFs are often the most accessible, affordable and convenient foods to consume.
"Changing the food environment to help people access healthier, more minimally processed foods is an important part of the solution," Page said.
Because the study was observational, it cannot establish whether UPF consumption causes changes in brain activity or weight gain. To test cause and effect, Page aims to conduct an intervention study where children who regularly eat UPFs are given more minimally processed foods. Researchers could then track whether their brain responses to food images change over time and whether those changes are associated with less weight gain.
The BrainChild study will also continue to follow children through puberty into young adulthood, documenting brain changes, body composition and links between diet and overall health.
About this research
In addition to Page, the study's other authors are Jasmin M. Alves, Ella Morgan, Brendan Angelo, Kianna Le and Jared Smith from the Division of Endocrinology and Diabetes, Department of Medicine and the Diabetes and Obesity Research Institute, Keck School of Medicine of USC, University of Southern California; Kay Jann from the USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California; and Ting Chow and Anny H. Xiang from the Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California.
This research was supported by an American Diabetes Association Pathway Accelerator Award [1-14-ACE-36]; the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (NIH) [R01DK116858, R01DK134079]. The REDCap database used for this study was supported by the Southern California Clinical and Translational Science Institute [NIH UL1TR001855].
