Impact of Exercise on Brain Responses to Visual Food Cues: An fMRI Study

On the basis of a strong body of data, the Institute of Medicine currently recommends at least 60 minutes of exercise per day to prevent body weight gain overtime. Previous studies have shown that there is no compensatory increase in food intake with this dose of exercise. Ultimately, the brain decides whether to alter food intake. Surprisingly, no published studies have assessed the impact of exercise on brain activation. Using functional magnetic resonance imaging (fMRI) and an appetite questionnaire, we investigated the effects of a single bout of aerobic exercise on brain responses to visual food cues and subjective appetite responses. After an overnight fast, 30 (17M, 13W), healthy, habitually active subjects (22.0±3.8 years, 23.6±2.4 kg/m2, 44.3±8.3 mL∙kg-1∙min-1) either rested or exercised for 60 minutes, in a counterbalanced crossover design. Immediately after each condition, blood oxygen dependent levels were determined in response to visual food cues of different energy value during an fMRI scan. Exercise showed significantly greater activation (P \u3c .005, uncorrected) in regions implicated in food inhibition (superior frontal gyrus, medial surface), and visual attention (precuneus, superior temporal gyrus, middle temporal gyrus and fusiform gyrus) regions. However, exercise did show a greater activation in a food reward region (medial orbitofrontal cortex). The rest condition only showed greater activation in a visual center (fusiform gyrus) and the midbrain. In addition, relative to no-exercise, subjective appetite responses were suppressed following the exercise bout. Taken altogether, these data suggest exercise may impact the brain in a direction expected to suppress food intake and increase food attention, which is in line with previous behavioral, biological and fMRI data. These findings may explain, at least partially, why aerobic exercise does not lead to a compensatory increase in food intake