Relationships between insulin sensitivity, skeletal muscle mass and muscle quality in obese adolescent boys.

We examined the relationships between insulin sensitivity (IS), skeletal muscle (SM) mass and SM quality in youth. Forty obese adolescent boys (body mass index ≥ 95 th percentile, 12-18 years) participated in this study. IS and glucose tolerance was measured by a 3 h hyperinsulinemic-euglycemic clamp and a 2 h oral glucose tolerance test (OGTT), total SM mass and intermusular adipose tissue (IMAT) by whole-body magnetic resonance imaging, and muscular strength by one-repetition maximum leg and bench press. IMAT was associated (P<0.05) with IS (r=-0.53) and OGTT-insulin area under the curve (AUC; r=0.31). Similarly, muscular strength was associated (P<0.05) with both IS (r=0.39) and OGTT-insulin AUC (r=-0.32). By contrast, total SM mass was not associated with IS or any OGTT parameters (P>0.1). After accounting for race and tanner stage, IMAT and muscular strength remained significantly associated with IS, together explaining a total of 41% of the variance in IS. Our findings suggest that SM quality, but not SM mass, is associated with IS in obese adolescent boys.