Evening high‐intensity interval exercise does not disrupt sleep or alter energy intake despite changes in acylated ghrelin in middle‐aged men

New Findings

What is the central question of this study?

High‐intensity interval exercise (HIIE) is recommended to be avoided within 4 h of bedtime due to potential sleep disruptions which may affect appetite‐related hormone interactions and subsequent energy intake. Yet, the interactions between sleep and appetite following early evening HIIE has not been previously explored.

What is the main finding and its importance?

We show that HIIE can be performed in the early evening without subsequent sleep disruptions and may favourably alter appetite‐related hormone concentrations. Nonetheless, perceived appetite and energy intake do not change with acute HIIE regardless of time‐of‐day.

Abstract

Many adults remain inactive, despite exercise benefits for sleep and appetite, due to increased time‐restraints. Methods to improve exercise compliance include preferential time‐of‐day or engaging in short‐duration, high‐intensity interval exercise (HIIE). Hence, this study aimed to compare effects of HIIE time‐of‐day on sleep and appetite. Eleven inactive men undertook sleep monitoring to determine baseline (BASE) sleep stages and exclude sleep disorders. On separate days, participants completed 30 min HIIE (60 s work at 100% V̇O_2peak: 240 s rest at 50% V̇O_2peak) in the 1) morning (MORN; 0600–0700 h), 2) afternoon (AFT; 1400–1600 h) and 3) early evening (EVEN: 1900–2000 h). Measures included appetite‐related hormones (acylated ghrelin, leptin, peptide tyrosine tyrosine), and glucose pre‐exercise, 30 min post‐exercise, and next morning; overnight polysomnography (PSG; sleep stages); and actigraphy, self‐reported sleep and food diaries for 48 h post‐exercise. There were no between‐trial differences for total sleep time (p = 0.46). Greater stage N3 sleep was recorded for MORN (23 ± 7%) compared to BASE (18 ± 7%; p = 0.02); however, no between‐trial differences existed (p > 0.05). Rapid eye movement (REM) sleep was lower and non‐REM sleep was higher for EVEN compared to BASE (p ≤ 0.05). At 30 min post‐exercise, ghrelin was higher for AFT compared to MORN and EVEN (p = 0.01); while glucose was higher for MORN compared to AFT and EVEN (p ≤ 0.02). No between‐trial differences were found for perceived appetite (p ≥ 0.21) or energy intake (p = 0.57). Early evening HIIE can be performed without subsequent sleep disruptions and reduces acylated ghrelin. However, perceived appetite and energy intake appear to be unaffected by HIIE time‐of‐day.

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