Abstract P377: Insulin, Muscle Mass and Exercise Performance in Overweight Women

Abstract

Introduction Obesity is associated with many negative health impacts, including hyperinsulinemia and reduced exercise performance, despite being associated with greater lean skeletal mass which works as the insulin-targeting and exercising organ. Purpose of Study We delineated the associations amongst cardiorespiratory capacity, fat mass, skeletal mass distributions, and fasting plasma insulin in overweight, non-diabetic women. Methods One hundred and seventy-two sedentary women, age 22 to 68 years (range), body mass index (BMI) (34.2 ± 6.3 [mean ± SD]; range 25.3 to 57.6 kg/m 2 ), underwent dual energy x-ray absorptiometry for body composition, fasting insulin, and graded treadmill exercise test using the Bruce protocol with measurement of oxygen consumption (peak VO 2 ). Results After adjustment for age, fasting insulin (9.8 ± 8.1; range 1.9 to 47.6 mcU/ml) was positively associated with BMI (r = 0.43, p<0.001), fat mass (r = 0.41, p< 0.001), load-bearing skeletal muscle mass (lower extremity lean mass; r = 0.29, p< 0.001), and non-load-bearing skeletal muscle mass (upper extremity lean mass; Figure, Panel A). By multiple regression analysis with age, fat mass and lower and upper extremity lean masses as covariates, fat mass, age and upper extremity lean mass (Figure, Panel B) were independent negative predictors of peak VO 2 (all p< 0.01). Lower extremity, however, trended to be positively predictive of peak VO 2 (p = 0.067). Conclusions In non-load-bearing muscle, increased lean mass associated with elevated plasma insulin is predictive of reduced oxygen consumption during exercise, suggesting additional load that may diminish cardiorespiratory exercise performance or intrinsic impairment in skeletal muscle function. In load-bearing muscle, compensatory hypertrophy due to increased fat and lean mass loads may preserve exercise performance.