Effects of time-restricted eating with exercise on body composition in adults: a systematic review and meta-analysis

BACKGROUND: The effects of time-restricted eating (TRE) with exercise on body composition in adults are not clear. OBJECTIVE: This meta-analysis aimed to assess the effects of TRE when followed in combination with various forms of exercise, including aerobic, resistance, and combined aerobic and resistance [concurrent] training on body composition. METHODS: Studies published up to May 2023 were searched in EBSCOhost (MEDLINE, CINAHL, SPORTSDISCUS), PubMed, and SCOPUS databases. Fifteen studies, including 338 participants, that evaluated TRE vs. unrestricted eating in individuals performing exercise were analyzed. A random-effects model was used to calculate the weighted mean effect sizes (ES) with 95% confidence intervals (95% CI's). RESULTS: According to the pooled results, TRE had a small but significant reduction of fat mass (FM) kg with an effect size of -0.20 (95% CI = -0.28 to -0.13, p < 0.001) and on body fat percent (BF%) with an effect size of -0.23 (95% CI = -0.35 to -0.11, p < 0.001). The prediction interval ranged from -0.48 to 0.08 for FM and from -0.64 to 0.18 for BF%, respectively. TRE did not significantly alter fat-free mass (FFM) kg compared to control (p = 0.07). Furthermore, age, body mass index (BMI), exercise type, study duration, and energy intake did not have a significant impact on the variation in effect sizes according to the subgroup analyses (p > 0.05). CONCLUSION: TRE with exercise may reduce fat mass compared to an unrestricted eating window exercise-matched control while preserving FFM. However, more studies are needed.