We examined the associations between thigh muscle area (TMA) and insulin resistance (IR) according to body mass index (BMI) in middle-aged Korean general population.

TMA was measured using quantitative computed tomography and corrected by body weight (TMA/Wt) in 1,263 men, 788 premenopausal women, and 1,476 postmenopausal women all aged 30 to 64 years. The tertiles of TMA/Wt were calculated separately for men and for premenopausal and postmenopausal women. Homeostatic model assessment for insulin resistance (HOMA-IR) was performed using fasting blood glucose and insulin levels, and increased IR was defined according to sex-specific, top quartiles of HOMA-IR. Associations between the TMA/Wt tertiles and increased IR according to the BMI categories (<25 and ≥25 kg/m2) were assessed using multivariable logistic regression analysis.

In men with higher BMIs, but not in those with lower BMIs, the presence of an increased IR had significantly higher odds ratios in the lower TMA/Wt tertiles, even after adjustment for visceral fat area. However, in premenopausal and postmenopausal women, there was no significant inverse association between TMA/Wt tertiles and increased IR, regardless of BMI category.

Our findings suggest that the thigh muscle is inversely associated with IR in men, particularly in those with higher BMIs.