Effects of exercise timing and metabolic state on post-exercise energy intake and appetite-a randomized crossover trial.

BACKGROUND

Exercise timing and metabolic state influence post-exercise energy balance, yet their combined effects remain incompletely understood.

OBJECTIVES

To disentangle the effects of time of day (morning compared with evening) and nutritional state (fasted compared with fed) on post-exercise energy intake and appetite.

METHODS

In a randomized crossover design, 35 healthy young adults completed 3 fasted exercise conditions: morning after a 12 h overnight fast (12 h AMEx) and evening after a 12 h (12 h PMEx) or 6-h fast. A subsample (n = 17) additionally completed fed morning and fed evening exercise. Each session was 30 min of treadmill running at 65% V̇O2peak. Substrate oxidation was quantified by indirect calorimetry, acute energy intake via an ad libitum test meal, and 24-h intake by weighed food records. Appetite was assessed before and after exercise. Linear mixed models were used throughout.

RESULTS

Relative to morning (12 h AMEx), evening fasted exercise (12 h PMEx) increased acute intake by 400 kcal [95% confidence interval (CI): 286, 515 kcal] and 24-h intake by 547 kcal (95% CI: 335, 759 kcal; both P < 0.001). Shortening the pre-exercise fast from 12 to 6 h before evening exercise attenuated acute but not 24-h intake. Hunger, desire to eat, and prospective consumption were higher, and fullness lower, after evening than morning exercise, mirroring intake. Fat oxidation was greater during fasted and evening exercise conditions; 12 h PMEx exceeded 12 h AMEx by 0.77 kcal/min (95% CI: 0.37, 1.17 kcal/min; P < 0.001). Pre-exercise feeding suppressed fat oxidation but did not attenuate energy intake or appetite.

CONCLUSIONS

Evening-fasted exercise induces pronounced compensatory eating and elevated 24-h appetite, despite greater fat oxidation. Pre-exercise feeding alters substrate use but does not reduce intake, underscoring a dissociation between metabolic and behavioral regulation and the primacy of timing in post-exercise appetite control. This trial was registered at clinicaltrials.gov as NCT06947824.