Abstract

This study examined the effect of an 8-week, progressive exercise intervention on neural responses, specifically N2 amplitude as a measure of inhibitory control, to pictures of food. Healthy women ages 18-44 years were randomized to a morning (AM) exercise group or evening (PM) exercise group. The AM group did moderate-to-vigorous intensity exercise on 4 days per week between 6:30 and 9:30 a.m. while the PM group had the identical volume of exercise between 6:30 and 9:30 p.m. Neural responses, eating behaviors, cardiovascular fitness outcomes, and body weight/composition were measured at baseline and after the 8-week intervention. The N2 amplitude in response to pictures of high- and low-calorie foods was assessed using electroencephalography during a go/no-go task. Dietary restraint, emotional eating, and external eating were assessed using the Dutch Eating Behavior Questionnaire. VO_2peak, HR_max, and time to completion were measured during a maximal treadmill test. Body weight was measured on a digital scale, and body composition was measured using dual-energy x-ray absorptiometry. There was not a significant task (go, no-go) × group (AM, PM) × period (baseline, 8 weeks) interaction (F = 0.18; p = 0.677), but there was a main effect of exercise over 8 weeks (F = 6.26; p = 0.017) with increased N2 amplitude following the intervention. There was not a significant interaction as a function of picture type (high-calorie, low-calorie), task, group, and period (F = 0.52; p = 0.478). Changes in body weight and neural outcomes were not significantly associated with changes in eating behaviors for either group (ps < 0.05). There was a significant group × period interaction for body weight (F = 4.90; p = 0.032). Body weight increased by 0.79 ± 1.16 kg in the AM group and decreased by 0.21 ± 1.46 kg in the PM group (effect size = 0.77; CI = 0.15-1.35). There was not a significant group × period interaction for body fat percentage, total body fat or fat-free mass (ps < 0.05). When examining the main effect of exercise on cardiovascular fitness outcomes, VO_2peak was not different (F = 1.80; p = 0.187), time-to-completion on treadmill increased (F = 6.51; p = 0.014), and HR_max during the treadmill test was significantly lower (F = 5.49; p = 0.025). This study suggests that 8 weeks of exercise training may increase the inhibitory response to pictures of both high- and low-calorie foods. However, time of day of exercise did not influence this response. Eight weeks of exercise training did not change self-reported dietary restraint, external eating, or emotional eating, and there was no correlation between these eating behaviors and inhibitory control. However, evening exercise was more beneficial for body weight than morning exercise. Given the novelty of this study and its results, additional studies on the influence of time of day of exercise on weight management are needed.

Degree

College and Department

Life Sciences; Exercise Sciences

Rights

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