Synergistic effect of long-term L-citruline supplementation combined with exercise on body composition in adults: A systematic review and meta-analysis of randomized controlled trials

This study aims to systematically evaluate the synergistic effects of long-term supplementation of L-citrulline combined with exercise on body composition in adults through a meta-analysis. This study primarily summarized and analyzed outcome indicators including body weight (BW) , body mass index (BMI), body fat (BF) (including fat mass [FM] and body fat percentage [BFP]), android fat mass (AFM), gynoid fat mass (GFM), and total lean mass (TLM). Statistical analyses were performed using RevMan (Version 5.4) software provided by the Cochrane Collaboration. For continuous variables, the pooled effect sizes were expressed as standardized mean differences (SMD) with their 95% confidence intervals (CI). A total of 9 randomized controlled trials (RCTs) were included that investigated the effects of long-term supplementation of L-citrulline combined with exercise on body composition in adults. The results indicated that, compared to exercise alone, L-citrulline supplementation combined with exercise significantly improved BF (SMD = -0.21, 95% CI: -0.40 to -0.01, P = 0.03) and AFM (SMD = -0.32, 95% CI: -0.57 to -0.07, P = 0.01). However, no significant effects were observed on BW (SMD = -0.01, 95% CI: -0.27 to 0.25, P = 0.95), BMI (SMD = 0.01, 95% CI: -0.31 to 0.33, P = 0.93), GFM (SMD = -0.17, 95% CI: -0.42 to 0.08, P = 0.18), and TLM (SMD = -0.02, 95% CI: -0.23 to 0.19, P = 0.83). This study is the first to demonstrate through a meta-analysis that long-term supplementation of L-citrulline combined with exercise can synergistically improve BF and AFM in adults. • This study is the first to confirm through meta-analysis that long-term L-citrulline supplementation combined with exercise has a synergistic effect on improving body composition (fat) in adults. • The combined intervention significantly reduces total fat mass and is particularly effective in decreasing android fat mass, demonstrating a specific improvement effect on central obesity. • The combined intervention did not significantly affect overall body weight, body mass index, hip fat mass, or total lean body mass, indicating that its primary effect resides in regulating fat metabolism rather than inducing broad changes in body composition. • This research provides important scientific evidence for the use of L-citrulline as a sports nutrition supplement aimed at the targeted optimization of body composition, particularly in promoting fat metabolism.