Low leg fat mass is associated with low insulin sensitivity, inflammatory markers, and β-cell dysfunction in non-obese Japanese people.

We tested whether leg fat mass is associated with insulin sensitivity, metabolic syndrome components, inflammatory markers, and impaired pancreatic β-cell function in a setting where body composition is less related to socioeconomic status. Leg fat (relative to body fat) by DXA, surrogate measures of insulin sensitivity and pancreatic β cell function inferred from serum insulin kinetics during a 75 g oral glucose tolerance test (OGTT), metabolic syndrome components, and inflammatory markers, were measured in middle-aged Japanese parents of university students, whose BMI averaged < 23.0 kg/m2 and homeostasis model assessment insulin resistance (HOMA-IR) < 1.5. Low leg fat was associated with high HOMA-IR, adipose insulin resistance index (a product of fasting insulin and free fatty acid), OGTT-derived hepatic insulin resistance, and low Matsuda index. In addition, low leg fat was associated with a low disposition index (insulin resistance-adjusted insulin secretion) and high fasting and post-glucose glycemia. Further, it was related to high triglycerides, blood pressure, liver enzymes, and low HDL cholesterol. Finally, low leg fat was associated with high C-reactive protein and orosomucoid, acute phase proteins, and high leucocyte counts. The present study suggests that the percentage leg fat mass should be considered in assessing cardiometabolic risk stratification.