Purpose: This study examined the effect of a bout of moderate-to-vigorous (MV) exercise on the neural response to pictures of food (used to index food motivation) in normal-weight and obese women. Secondary outcomes included energy intake and physical activity (PA) over 24 h.
Methods: Using a crossover design, 18 normal-weight and 17 obese women completed a morning-time, 45-min exercise bout (treadmill at 3.8 mph; 0% grade) and were subsequently followed for 24 h. This was counterbalanced by a control day with no exercise bout. To assess the effect of exercise on food motivation, participants were shown pictures of food and flowers (control) after exercise. Neural activity was concurrently monitored using electroencephalogram for the late positive potential (LPP) component of the event-related potential (ERP) and compared with the LPP response on the nonexercise day. After testing, weighed food records were kept for the duration of each day. PA was monitored, via accelerometry, over each day.
Results: There was not a significant body mass index (BMI) group × exercise condition × picture-type interaction for LPP amplitude; however, when participants were pooled, the exercise condition resulted in lower LPP amplitude waveforms in response to food pictures than the nonexercise condition (F = 4.25, P = 0.048). There were no differences in energy or macronutrient intake (P > 0.05). The exercise condition resulted in significantly more PA than the nonexercise condition, and there was a significant BMI group × exercise condition interaction for MV PA (F = 4.48, P = 0.043) with obese women showing less MV PA.
Conclusions: A bout of MV exercise decreases neurologically determined food motivation (i.e., the LPP event-related potential), but the effect of BMI is unclear. In addition, a morning-time exercise bout significantly increases 24-h PA; 24-h MV PA differed according to BMI.