Insulin resistance and changes in body composition are side effects of androgen deprivation therapy (ADT) given to prostate cancer patients. The present study investigates if endurance training improves insulin sensitivity and body composition in ADT-treated prostate cancer patients. Nine men undergoing ADT for prostate cancer and 10 healthy men with normal testosterone levels underwent 12 weeks of endurance training. Primary endpoints were insulin sensitivity (euglycemic hyperinsulinemic clamps with concomitant glucose-tracer infusion) and body composition (dual-energy x-ray absorptiometry and magnetic resonance imaging). The secondary endpoint was systemic inflammation. Statistics: Two-way ANOVA. Endurance training increased VO2max (ml(O2)/min/kg) by 11% and 13% in patients and controls, respectively (p