Influence of Ultra-processed Foods on Reward Processing and Energy Intake

Most individuals with obesity become so before age 35. In the US population, adolescents have the highest ultra- processed food consumption (68% of total energy) and the lowest diet quality. Given that ultra-processed foods represent two-thirds of the energy consumed by adolescents and young adults, research is needed to understand the influence of food processing on eating behaviors, particularly in the late adolescence and early adulthood life stage. During this time, individuals have increasing independence in food choice and it represents a key developmental period for executive function, processes that affect life-long mental and physical health. Evidence from pre-clinical studies demonstrates rodents maintained on a "cafeteria diet" comprised of ultra- processed ingredients have greater energy intake, weight gain, and alterations in brain circuitry that regulates both energy intake and executive function than those exposed to a standard diet. However, the impact of ultra- processed foods on the brain circuits underlying reward processing, food intake regulation, food choice, and executive function in humans is unknown. Controlled diet interventions are needed to fill this void. The overall objective of this research is to establish proof-of-concept for altered reward processing measured by brain response to an ultra-processed milkshake, an increase in ad libitum energy intake in a buffet meal, and adverse effects on executive function in response to a diet high in ultra-processed foods (81% total energy) compared to a diet emphasizing un/minimally-processed foods in individuals aged 18-25 years. To address our objective, 32 individuals aged 18-25 years (late adolescence/early adulthood) (BMI<30) will undergo two 14-day controlled feeding conditions in a randomly assigned order. Diets will match the caloric needs of the individual and be matched for potential confounding factors including macronutrients, fiber, and energy density. To assess changes in reward processing, brain response to an ultra-processed milkshake will be assessed via functional magnetic resonance imaging before and after each feeding period (4 measurements). Measurements immediately following each feeding period will include ad libitum energy intake and food selection at a breakfast buffet meal (containing both ultra-processed and minimally processed foods), eating in the absence of hunger post-meal, and executive function. Although consumption of ultra-processed foods may contribute to dysregulation of energy intake, mechanisms are uncertain and existing dietary guidelines do not address ultra- processed food intake due to a lack of human experimental research. The proposed research could address this gap and inform dietary guidelines for individuals at a critical developmental life stage - late adolescence to early adulthood.