Association between muscle mass and insulin sensitivity independent of detrimental adipose depots in young adults with overweight/obesity

BACKGROUND/OBJECTIVE: Less muscle mass has been associated with greater insulin resistance, but whether the association is independent of deleterious adipose depots in young adults with overweight/obesity who are at high risk for type 2 diabetes (T2DM) but are otherwise metabolically healthy is not known. The objective of this study was to determine whether muscle mass is independently associated with insulin sensitivity (IS) in young adults with overweight/obesity. SUBJECTS/METHODS: Cross-sectional Clinical Research Center study of 132 adults, 21–45yo, BMI ≥25 kg/m(2) and metabolically healthy without T2DM. Primary independent variable: percent ideal appendicular lean mass (ALM) calculated as measured ALM divided by predicted ALM for age, weight, and height, calculated using validated NHANES data-based equation. Primary dependent variable: IS by Matsuda index. RESULTS: Mean age was 34.3±6.8 years, and mean BMI 35.8±5.8 kg/m(2) (mean±SD). Individuals in the highest % ideal ALM tertile had mean IS 45% higher than the lowest tertile [6.94±0.85 vs 4.80±0.56 (mean±SEM), p=0.008](sex interaction p=0.003). Men in the highest % ideal ALM tertile had mean IS twice the lowest tertile (5.47±0.68 vs 2.68±0.34, p=0.001), which remained significant controlling for visceral/subcutaneous and intermuscular adipose tissue, and intramyocellular and intrahepatic lipids (p=0.03). The association was not significant in women. CONCLUSIONS: Muscle mass is associated with IS independent of detrimental adipose depots in young men with overweight/obesity, at risk for T2DM but currently metabolically healthy. Muscle mass relative to sex, age, weight, and height-specific norms may be used to ascertain individual T2DM risk associated with low muscle mass.