Effects of diurnal exercise timing on appetite, energy intake and body composition: A parallel randomized trial

Objective To determine the effect of diurnal exercise timing on appetite, energy intake and body composition in individuals with overweight or obesity. Methods Forty sedentary, individuals with overweight or obesity (17 males, 23 females; age: 51 ± 13 years; BMI: 30.9 ± 4.2 kg/m2) were randomly allocated to complete a 12-week supervised multi-modal exercise training program performed either in the morning (amEX) or evening (pmEX). Outcome measures included appetite in response to a standardised test meal, daily energy intake (EI), body weight and body composition. Measures of dietary behaviour were assessed at baseline and post-intervention, along with habitual physical activity, sleep quality and sleep quantity. Significance was set at p ≤ .05 and Hedge's g effect sizes were calculated. Results Regardless of timing, exercise training increased perceived fullness (AUC; g = 0.82–1.67; both p < .01), decreased daily EI (g = 0.73–0.93; both p < .01) and body-fat (g = 0.29–0.32; both p <. 01). The timing of exercise did not change the daily EI or body-fat response to training (all p ≥ .27), however, perceived fullness increased in the amEX group (p ≤ .01). Disinhibition (g = 0.35–1.95; p ≤ .01) and Hunger (g = 0.05–0.4; p = .02) behaviours decreased following exercise training, with Disinhibition demonstrating greater improvements in the pmEX group (p = .01). Objective and subjective sleep quantity increased with training (all p ≤ .01), but sleep quality was not reported to change. Conclusions Multi-modal exercise training improved body composition and some appetite outcomes, although changes were inconsistent and largely independent of exercise-timing. In the absence of dietary manipulation, the effect of diurnal exercise timing on appetite and body composition appear trivial compared to the overall benefits of exercise participation.