Effects of evening exercise on anthropometric indices, metabolic profiles, and sleep health: a systematic review and meta-analysis.

BACKGROUND

Evening exercise may elevate arousal levels and enhance insulin sensitivity, potentially influencing sleep hygiene and metabolic profiles. To gain a clearer understanding of these effects, we conducted a meta-analysis to compare the impact of morning versus evening exercise on anthropometric indices, metabolic markers, and sleep health.

METHODS

A systematic search of the MEDLINE, EMBASE, and Cochrane databases was conducted from inception through March 2023. Exercise is defined as physical activity performed at a minimum of moderate intensity. For the outcomes of interest, mean differences (MD) and 95% confidence interval (CI) were calculated using a random-effects model.

RESULTS

A total of 716 participants were included across 14 studies, comprising both randomized controlled trials and observational studies. Of these, 11 studies reported anthropometric indices, 8 reported metabolic profiles, and 5 evaluated sleep parameters. No significant associations were observed between exercise timing and the health outcomes assessed. Specifically, there were no notable differences in body weight (MD:-0.12 kg [95% CI -0.99 to 0.76, I2= 99%]) or body mass index (MD: -0.07 kg/m2 [95% CI -0.58 to 0.44, I2 = 99%]) between morning and evening exercise sessions. Sleep latency was also unaffected by exercise timing (MD: -2.24 minutes [95% CI-10.22 to 5.74, I2 = 99%]). Additionally, metabolic biomarkers, including low-density lipoprotein (MD: 0.11 mmol/L [95% CI -0.37 to 0.58, I2= 100%]), and high-density lipoprotein (MD: 0.09 mmol/L [95% CI -0.05 to 0.22, I2 = 99%]), showed no significant differences based on exercise timing.

CONCLUSION

This meta-analysis found no significant association between the timing of exercise and health outcomes, including anthropometric measurements, metabolic markers, and sleep parameters. While the findings are hypothesis-generating, they suggest that the timing of exercise may not substantially influence patient health outcomes and should be considered flexibly in clinical recommendations.