Appetite, energy intake and resting metabolic responses to 60min treadmill running performed in a fasted versus a postprandial state

This study investigated the effect of fasted and postprandial exercise on appetite, energy intake and resting metabolic responses. Twelve healthy males (mean±SD: age 23±3years, body mass index 22.9±2.1kgm^-2, maximum oxygen uptake 57.5±9.7mLkg^-1min^-1) performed three 10h experimental trials (control, fasted exercise and postprandial exercise) in a Latin Square design. Trials commenced at 8am after an overnight fast. Sixty min of treadmill running at ∼70% of maximum oxygen uptake was performed at 0-1h in the fasted exercise trial and 4-5h in the postprandial exercise trial. A standardised breakfast was provided at 1.5h and ad libitum buffet meals at 5.5 and 9.5h. Appetite ratings and resting expired air samples were collected throughout each trial. Postprandial exercise suppressed appetite to a greater extent than fasted exercise. Ad libitum energy intake was not different between trials, resulting in a negative energy balance in exercise trials relative to control after accounting for differences in energy expenditure (control: 9774±2694kJ; fasted exercise: 6481±2318kJ; postprandial exercise: 6017±3050kJ). These findings suggest that 60min treadmill running induces a negative daily energy balance relative to a sedentary day but is no more effective when performed before or after breakfast.