Planned aerobic exercise increases energy intake at the preceding meal

Purpose Effects of exercise on subsequent energy intake are well documented, but whether pre-exercise energy intake is affected by future planned exercise is unknown. This study investigated the effect of planned late-afternoon exercise on appetite and energy intake before (breakfast and lunch) and after (evening meal/snacks) exercise.

Methods Twenty healthy, active participants (10 male; age 23 ± 5 y, BMI 23.7 ± 3.2 kg/m2, VO2peak 44.1 ± 5.4 ml/kg/min) completed randomised, counterbalanced exercise (EX) and resting (REST) trials. After trial notification, participants were provided ad libitum breakfast (0800 h) and lunch (1200 h) in the laboratory, before completing 1-h exercise (30 min cycling, 30 min running) at 75-80% maximal HR (EX; 2661 ± 783 kJ) or 1-h supine rest (REST; 310 ± 58 kJ) 3-h post-lunch. Participants were provided a food pack (pasta meal/snacks) for consumption post-exercise (outside laboratory). Appetite was measured regularly and meal and 24-hour energy intake quantified.

Results Ad-libitum energy intake was greater during EX at lunch (EX 3450 ± 1049 kJ; REST 3103 ± 927 kJ; P=0.004), but similar between trials at breakfast (EX 2656 ± 1291 kJ; REST 2484 ± 1156 kJ; P=0.648) and dinner (EX 6249 ± 2216 kJ; REST 6240 ± 2585 kJ; P=0.784). Total 24-hour energy intake was similar between trials (P=0.388), meaning relative energy intake (24-h energy intake minus EX/REST energy expenditure), was reduced during EX (EX 9694 ± 3313 kJ; REST 11517 ± 4023 kJ; P=0.004).

Conclusion Energy intake appears to be increased in anticipation of, rather than in response to, aerobic exercise, but the increase was insufficient to compensate for energy expened during exercise, meaning aerobic exercise reduced energy balance relative to rest.