The Impact of Controlled Diets High-In and Free of Ultra Processed Foods on Behavior and Brain in Emerging Adulthood

Abstract

Ultra-processed foods (UPF) comprise over half of the American diet and have been linked to poor health outcomes. Adolescence and young adulthood represent critical periods of executive function development, during which UPF consumption is highest. This crossover randomized controlled feeding trial examined the effects of UPF consumption on cognition, brain function, and eating behavior in individuals aged 18–25 years. Participants completed two 14-day controlled diet conditions in random order: a high UPF diet (81% energy from UPF) and a NonUPF diet (0% energy from UPF). Cognitive testing and functional magnetic resonance imaging (fMRI) were conducted before and after each diet to assess executive function, delay discounting, and brain response to milkshake. Following each intervention, participants completed an ad libitum buffet meal containing matched UPF and NonUPF foods to evaluate eating behavior. Removal of UPF from the diet improved inhibitory control as measured by the Flanker task. In adolescents (18–21 years), orbitofrontal cortex (OFC) response to milkshake consumption decreased following the UPF diet and increased following the NonUPF diet, whereas young adults (22–25 years) showed no changes. Habitual UPF intake was positively associated with OFC response independent of experimental diet condition. Additionally, entorhinal cortex response predicted subsequent energy intake at the buffet meal. Together, these findings demonstrate that UPF consumption may alter executive function, food valuation, and eating behavior in adolescents and young adults.