Resistance training performed in the fasted state compared to the fed state on body composition and strength in adults: A systematic review with meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of clinical trials
PubMed 41316673 · doi:10.1016/j.jbmt.2025.08.003
What was done
A systematic review and random-effects meta-analysis of clinical trials compared resistance training performed in a fasted state versus a fed state in adults. Databases, gray literature, and manual searches were conducted. Methodological quality was evaluated using a risk of bias tool for randomized trials. Outcomes evaluated were fat-free mass, body fat mass, muscle hypertrophy, and strength, expressed as standardized mean differences (SMD) with 95% confidence intervals (CI).
What was found
Four studies were analyzed, with three categorized as having a high risk of bias. Fasted resistance training resulted in significantly greater changes in body fat mass compared to fed training (SMD: -1.001; 95% CI: -1.970 to -0.032; p = 0.043). No significant differences were observed for fat-free mass (SMD: 0.529; 95% CI: -0.801 to 1.859; p = 0.436), muscle hypertrophy (SMD: 0.645; 95% CI: -0.753 to 2.042; p = 0.366), or strength (SMD: 0.415; 95% CI: -0.399 to 1.228; p = 0.318).
Why it matters
These results indicate that lifting weights while fasted does not impair muscle mass or strength adaptations relative to training fed, and may provide an additional benefit for fat loss.
Limits
The total sample of studies is very small (n = 4), and three of the four trials carried a high risk of bias. Confidence intervals for hypertrophy, fat-free mass, and strength were very wide, and the total participant count was not reported in the abstract.