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/m) 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.