Study Reveals Why Ultra-Processed Foods Make Teens Overeat Even Without Hunger - Video

Why do young people find it so hard to stop snacking on chips or fast food? A new study from Virginia Tech suggests the answer may lie in how ultra-processed foods affect the adolescent brain. Researchers found that 18- to 21-year-olds ate more—and even when they weren’t hungry—after just two weeks on a highly processed diet, while slightly older young adults did not show the same response. The findings, published in Obesity, highlight adolescence as a critical window when food choices may “train” long-term eating behavior.

Ultra-processed foods—like packaged snacks, sugary drinks, and frozen meals—make up over 60% of the average young American’s diet. These foods are loaded with additives and engineered for flavor and convenience, but research increasingly links them to obesity, diabetes, and heart disease. The Virginia Tech team, led by Dr. Brenda Davy and Dr. Alexandra DiFeliceantonio, set out to test whether exposure to these foods changes how much young people eat, particularly when they aren’t physiologically hungry.

They recruited 27 men and women aged 18 to 25 whose weight had remained stable for six months. Each participant followed two carefully designed diets—one rich in ultra-processed foods (81% of calories) and one completely free of them—each lasting two weeks, separated by a month-long break. To ensure fairness, the diets were matched on 22 nutritional factors, including calories, sugar, fat, and vitamins.

After each diet period, participants were invited to a buffet-style breakfast and told to eat freely. They were later offered snacks to test “eating without hunger.” Overall, total intake didn’t change much—until the researchers broke the data down by age. Participants aged 18–21 consumed significantly more calories after the ultra-processed diet and were more likely to continue snacking when full, compared to the 22–25 group.

The results suggest that the younger brain may be especially sensitive to processed foods, possibly because reward and self-control circuits are still developing during late adolescence. The team plans to expand their research to larger groups and use brain imaging to understand how processed diets influence appetite control.

For now, the takeaway is clear: what young adults eat today may shape how their bodies—and brains—respond to food tomorrow.

REFERENCE: Maria L. M. Rego, Emma Leslie, Emily Schmall, Bailey Capra, Summer Hudson, Monica L. Ahrens, Benjamin Katz, Kevin P. Davy, Valisa E. Hedrick, Alexandra G. DiFeliceantonio, Brenda M. Davy. The Influence of Ultraprocessed Food Consumption on Energy Intake in Emerging Adulthood: A Controlled Feeding Trial. Obesity, 2025; DOI: 10.1002/oby.70086