Time-restricted eating and weight: what 20 trials found

A 2025 meta-analysis of 20 randomised trials (1,242 adults) pooled a body weight 1.59 kg lower with time-restricted eating (TRE) than with unrestricted eating. Fat-free mass, which includes muscle but also water and organs, was 0.58 kg lower as well. The abstract words its conclusion on adding TRE to calorie restriction differently from its pooled estimate, which the sections below set side by side.

What did the time-restricted eating meta-analysis pool?

Sun et al., Int J Behav Nutr Phys Act 2025 searched five databases for trials published before July 2024 in which participants fasted at least 12 hours a day, six or more days a week. Interventions lasted 4 to 52 weeks. Eleven of the 20 studies enrolled people with overweight or obesity.

For TRE alone versus no restriction, the pooled weighted mean differences were -1.59 kg for body weight (95% CI -2.02 to -1.15), -0.93 kg for fat mass (-1.22 to -0.63) and -0.58 kg for fat-free mass (-0.81 to -0.36). Heterogeneity for body weight was high (I-squared 78%), and about half of the trials raised some risk-of-bias concerns.

What happens when a time window is added to calorie restriction?

In trials comparing TRE plus energy restriction with energy restriction alone, the pooled differences were -0.94 kg for body weight (95% CI -1.58 to -0.31, p = 0.004), -1.13 kg for fat mass (-1.50 to -0.75) and -0.56 kg for fat-free mass (-0.81 to -0.31).

The abstract nonetheless concludes that combining TRE with energy restriction “has no additional beneficial effects on weight loss”. The paper’s results text also reports that difference as significant, so both statements appear in the same paper.

Fat-free mass fell by a similar amount in both comparisons, about 0.56 to 0.58 kg. That is a reminder that lean tissue can change alongside fat during weight loss, a theme also seen with GLP-1 medicines. The measure is not muscle alone, and the authors say the fat-free mass findings need further validation. Few trials reported energy intake, so the analysis cannot show whether any benefit came from the eating window or from eating less.

The bottom line

• Across 20 randomised trials, TRE alone was followed by a pooled body weight 1.59 kg lower (95% CI 1.15 to 2.02 kg lower) than unrestricted eating.
• With energy restriction in both arms, the pooled body weight difference was 0.94 kg, although the abstract’s conclusion describes no additional benefit on weight loss.
• Fat-free mass was 0.56 to 0.58 kg lower in both comparisons, and heterogeneity between trials was high.