Timing of high-intensity intermittent exercise affects ad libitum energy intake in overweight inactive men

The present study sought to clarify the impact of exercise intensity and timing on energy intake and appetite-related blood variables. Fourteen inactive overweight men were included in the study. Firstly, maximal aerobic power (MAP) was measured. Then, participants randomly performed 5 experimental sessions consisting of 30 min of steady-state exercise (SSE) at 50% of MAP, high-intensity intermittent exercise (HIIE) with 30s repetitions at MAP and 30s of passive recovery or no exercise (CTRL). Sessions were performed 1h (SSE_1h and HIIE_1h) or 2.5h (SSE_2.5h and HIIE_2.5h) after the consumption of a standardized breakfast. An ad libitum buffet was offered 3.5h after the completion of the breakfast. Absolute energy intake (EI) and relative energy intake (REI) (relative energy intake = energy intake - energy expenditure from exercise) were measured. Appetite (hunger, fullness and desire for specific foods) scores and circulating concentration of insulin and IL-6 were determined at 1h, 1.75h, 2.5h and 3.25h after breakfast while lactate was measured post-exercise. EI was greater after the CTRL session compared to HIIE_2.5h (5045.9 ± 1873.5 kJ vs. 3716.1 ± 1688.7 kJ). REI was greater for the CTRL session (5045.9 ± 1873.5 kJ) than HIIE_1h (3386.5 ± 1660.1 kJ), HIIE_2.5h (2508.5 ± 1709.3 kJ) and SSE_2.5h (3426.6 ± 1788.0 kJ). Higher hunger scores were observed following the CRTL session with respect to those of HIIE_2.5h. Insulin and IL-6 concentrations were greater after HIIE_1h and SSE_1h with respect to those obtained after HIIE_2.5h, SSE_2.5h and CTRL. Lactate concentrations were higher in HIIE_1h and HIIE_2.5h compared to those of SSE_1h and SSE_2.5h. These results show that HIIE performed 2.5h after a breakfast reduced appetite (hunger scores) and EI through mechanism that need to be characterized. This approach can be applied to individuals aiming to create an energetic deficit.