Where body fat is stored may matter as much as how much weight a person carries. A systematic review and meta-analysis published in Diabetes, Metabolic Syndrome and Obesity found that multiple body composition measures, particularly central fat accumulation, were associated with type 2 diabetes mellitus (T2DM), while greater leg fat mass was associated with lower odds of disease.

The analysis reviewed observational studies identified through eight databases through July 31, 2025. A total of 36 studies involving 2,614,625 participants were included. Random-effects or fixed-effects models were used to pool effect sizes, while subgroup and sensitivity analyses explored heterogeneity. Study quality was assessed using the Agency for Healthcare Research and Quality and Newcastle-Ottawa Scale tools.

Fat-related measures showed several significant associations. Leg fat mass was associated with lower T2DM odds (OR, 0.54; 95% CI, 0.46-0.63; P<0.0001). Higher odds were reported with body fat mass (OR, 2.36; 95% CI, 1.39-4.02), trunk fat mass (OR, 1.35; 95% CI, 1.12-1.62), visceral fat area (OR, 3.18; 95% CI, 1.28-7.89), body fat percentage (OR, 1.67; 95% CI, 1.31-2.14), and fat mass index (OR, 1.17; 95% CI, 1.08-1.27) (all P<0.0001). Lower skeletal muscle mass index was associated with higher T2DM odds (OR, 1.46; 95% CI, 1.17-1.82; P=0.0007), while lean mass changes were not significant.

The findings suggest that abnormal fat mass, lower muscle mass, and unfavorable fat distribution were associated with T2DM. Body composition assessment may help refine risk stratification beyond body weight or body mass index alone.