Exercise and diet effects on delay discounting and related neurobiology in adults with overweight or obesity: A randomized trial

OBJECTIVE: This study compared effects of exercise training and diet on impulsivity-related behaviors as measured by delay discounting and related neurobiology in adults with overweight or obesity. We hypothesized that exercise versus diet would be associated with reduced delay discounting propensity (k) and increased response in brain regions involved in cognitive control (medial prefrontal cortex, anterior cingulate cortex, and bilateral anterior insulae). METHODS: Participants (N = 40) were randomized to 12 weeks of exercise training or diet intervention. At baseline and postintervention, they completed a delay discounting task during functional magnetic resonance imaging (fMRI) in fasted and fed (post-meal) conditions. Linear mixed effects models assessed fasted-fed intervention effects on k and brain response in regions of interest. Exploratory analyses assessed whole-brain, satiety-state-specific, and reaction time effects. RESULTS: Across groups, k and reaction time during delay discounting decreased and weight decreased from baseline to postintervention (p values ≤ 0.010). In exploratory fed-state whole-brain analyses, a group × session effect was observed in the right dorsolateral prefrontal cortex (p < 0.005), driven by exercise-associated changes. A similar group × session interaction effect was observed in the anterior cingulate cortex (p = 0.006), also driven by reductions in fed-state response. CONCLUSIONS: Both interventions altered delay discounting behaviors. Exercise training was associated with reduced fed-state engagement of brain regions involved in self-referential processing and regulation during decision-making.