Background: Although being overweight or obese is a significant risk factor for type 2 diabetes mellitus (T2DM), conventional measures like body weight and body mass index have limitations in distinguishing between muscle and fat. Body composition metrics have superior value in explaining metabolic heterogeneity. Objective: This study conducted the systematic review and meta-analysis to investigate the relationship between body composition (fat/muscle-related indicators) and T2DM. Methods: We conducted a systematic search of eight databases to identify observational studies reporting the relationship between body composition and T2DM up to July 31, 2025. To pool effect sizes, random/fixed-effects models were employed. Subgroup and sensitivity analyses explored heterogeneity sources. Study quality was assessed via the Agency for Healthcare Research and Quality and Newcastle-Ottawa Scale tools. Results: A total of 36 studies with 2,614,625 participants were included. Fat-related analyses demonstrated that leg fat mass reduces T2DM risk (OR = 0.54 0.46, 0.63, P < 0.0001), while body fat mass (OR = 2.36 1.39, 4.02, P < 0.0001), trunk fat mass (OR = 1.35 1.12, 1.62, P < 0.0001), visceral fat area (OR = 3.18 1.28, 7.89, P < 0.0001), body fat percentage (OR = 1.67 1.31, 2.14, P < 0.0001), and fat mass index (OR = 1.17 1.08, 1.27, P < 0.0001) increase the risk. Muscle-related analyses indicated that lower skeletal muscle mass index is a risk element for T2DM (OR = 1.46 1.17, 1.82, P = 0.0007), while lean mass changes showed no significant association. Conclusion: The results concluded that T2DM is associated with both abnormal fat/muscle mass and imbalanced fat distribution. Our findings highlighted that based on the results of body composition assessment, we can identify high-risk populations and develop personalized interventions to optimize T2DM prevention strategies. Keywords: type 2 diabetes mellitus, body composition, observational study, meta-analysis
Cao et al. (Wed,) studied this question.