This study explored the relationship between muscle fat infiltration derived from mid-thigh computed tomography (CT) scan, central fat distribution and insulin sensitivity in postmenopausal women. Mid-thigh CT scans were used to measure low attenuation muscle surface (LAMS) (0-34 Hounsfield units (HU)), which represented a specific component of fat-rich muscle. Whole-body insulin sensitivity (M/I) was evaluated by an euglycemic-hyperinsulinemic clamp. A group of 103 women aged 57.0 ± 4.4 years was studied. Women with higher levels of LAMS presented higher metabolic risk features, particularly elevated fasting, 2-h plasma glucose (2hPG) concentrations and diminished M/I (P