Does early time-restricted eating reduce body weight and preserve fat-free mass in adults? A systematic review and meta-analysis of randomized controlled trials

This meta-analysis evaluated whether weight loss caused by early time-restricted eating could promote fat mass loss while preserving fat-free mass, thereby leading to improvements in inflammation and metabolic health. Relevant randomized controlled trials (RCTs) published up to March 28, 2023, were identified in six databases, including PubMed, Web of Science, and Embase. We initially screened 1279 articles, thirteen RCTs with 859 patients were ultimately included. Compared with nontime-restricted eating, early time-restricted eating significantly reduced body weight (−1.84 kg [−2.28, −1.41]; I2 = 56 %; P < 0.00001), fat mass (−1.10 kg [−1.47, −0.74]; I2 = 42 %; P < 0.00001), waist circumstance (−3.21 cm [−3.90, −2.51]; I2 = 43 %; P < 0.00001), visceral fat area (−9.76 cm2 [−13.76, −5.75]; I2 = 2 %; P < 0.00001), and inflammation as measured by tumour necrosis factor-α (−1.36 pg/mL [−2.12, −0.60]; I2 = 42 %; P < 0.001). However, early time-restricted eating did not lead to a significant change in fat-free mass (−0.56 kg [−1.16, 0.03]; I2 = 59 %; P = 0.06). Subgroup analysis showed that the early time-restricted eating of the 16:08 (fasting-time versus eating-time) strategy had a superior effect on preserving fat-free mass (−0.25 kg [−0.68, 0.18]; I2 = 0 %; P = 0.25) while significantly reducing body weight (−1.60 kg [−2.09, −1.11]; I2 = 0 %; P < 0.001) and improving metabolic outcomes. Early time-restricted eating, especially 16:08 strategy, appears to be an effective strategy to decrease body weight, fat mass, abdominal obesity and inflammation, but less likely to decrease fat-free mass.