Is there a skeletal muscle mass threshold associated with the deterioration of insulin sensitivity in sedentary lean to obese postmenopausal women?

Aim: The purpose of this study was to determine an optimal cut-off point of skeletal muscle mass, using appendicular lean body mass (LBM) index, that identifies at risk individuals with deteriorated insulin sensitivity, using an established quantitative insulin sensitivity index (QUICKI) cut-off.

Methods: We performed a cross-sectional analysis in 231 lean and obese (BMI: 18.7-51.0 kg/m(2)) menopausal women. Fasting plasma glucose and insulin were obtained to calculate QUICKI as an index of insulin sensitivity. Skeletal muscle mass was measured as appendicular LBM by DXA and expressed as appendicular LBM index [appendicular LBM (kg)/height (m(2))]. Cut-offs were determined using receiver operating characteristic (ROC) curve analyses.

Results: The best cut-off value for skeletal muscle mass index to identify menopausal women with reduced insulin sensitivity was 7.025 kg/m(2) which had a sensitivity of 69.5% and specificity of 58.2%.

Conclusion: Our results suggest that sedentary postmenopausal women with an appendicular skeletal muscle mass index above 7.025 kg/m(2) may be at greater risk of insulin resistance. Prospective studies are needed to validate our result.