An Interval Exercise Bout Blunts the Effects of Overeating Following Cognitive Fatigue

Abstract

Individuals consume more calories in a single meal when mentally fatigued than when rested. This may contribute to a positive energy balance. Exercise can lead to negative energy balance. Also, an acute bout of exercise increases blood glucose and lactate levels and may promote hormones associated with satiety. These effects of exercise may offset a positive energy balance following a mentally fatiguing task. PURPOSE: This study assessed whether exercise following mental fatigue results in negative or neutral energy balance when compared to non-exercise conditions. METHODS: Participants were randomly assigned to a Mental Fatigue (MF) or Mental Fatigue + Exercise condition (MF+E). In addition, all participants completed a Baseline Rest (BR) condition consisting of no mental work or exercise. Visit order was counterbalanced. During the MF or MF+E visit, participants completed assessments of working memory, a 20 minute mentally fatiguing task, and either a 15 minute rest period (MF) or 15 minute interval exercise period (MF+E). The exercise period consisted of four 2:23 min intervals at approximately 84% VO2 max and three 1:43 min rest periods. Estimated oxygen uptake and measured blood lactate was used to estimate energy expenditure during exercise. Each visit ended with an ad libitum pizza lunch. A 2-way repeated measures ANOVA was used to compare eating behavior between groups, and univariate ANOVA was used to compare energy balance between groups. RESULTS: 16 participants (age = 19.3 ± 1.1; 94% female) have completed the protocol. The 2-way repeated measures ANOVA indicated amount of food consumed does not significantly differ between groups. The univariate ANOVA indicated energy balance between the MF and MF+E group did significantly differ [F(1,13) = 5.33, p = .038]. Compared to baseline condition, MF resulted in 39.8 ± +125.7 kcal positive energy balance but participants in the MF+E condition averaged a -119.1 ± 140.8 kcal negative energy balance. CONCLUSIONS: This is an ongoing study. Initial analysis indicates that an acute bout of high intensity interval exercise following mental fatigue may lead to negative energy balance and blunt mental fatigue’s effects on energy balance. These results suggest that an acute bout of exercise may be employed to offset positive energy balance following mentally fatiguing tasks.