Exercise-induced improvement in insulin sensitivity is not mediated by change in cardiorespiratory fitness.

Abstract

Although exercise-induced improvement in cardiorespiratory fitness (CRF) and reduction in abdominal obesity are putative mechanisms by which chronic exercise attenuates insulin resistance (1), the independent contribution of each is unknown. We therefore investigated whether improvement in abdominal obesity and/or CRF mediates the effect of exercise on insulin sensitivity in abdominally obese adults. Participants included sedentary, abdominally obese men and women who participated in two previously published exercise interventions (2,3). Participants were randomized to control ( n = 18) or supervised aerobic exercise ( n = 59) for 3 (women) or 4 (men) months. CRF (VO2peak) was measured using a maximal treadmill test, abdominal obesity by magnetic resonance imaging and waist circumference (WC), and insulin sensitivity by the hyperinsulinemic-euglycemic clamp. Simple mediation analysis (Table 1) revealed that with the exception of …