EFFECTS OF EXERCISE AND WEIGHT-LOSS ON LEUCINE TURNOVER IN DIFFERENT TYPES OF OBESITY

These studies were performed to determine whether protein turnover dur ing exercise and after weight loss is influenced by obesity and body f at distribution. Leucine carbon flux was measured before, during, and after 2.5 h of bicycle exercise in 10 upper body obese, 9 lower body o bese, and 6 nonobese, age-matched, premenopausal women. The obese wome n then followed an energy-restricted diet for 16 wk, resulting in appr oximately 8 kg weight loss. Baseline leucine carbon flux was greater ( P < 0.01) in obese women than in nonobese women but decreased in a sim ilar fashion in response to exercise in all groups. There were no diff erences between upper body and lower body obese women during exercise. After weight loss, baseline leucine carbon flux decreased (P < 0.05) similarly in both groups of obese women and was further suppressed by exercise. Thus obesity phenotype has no specific effect on either base line protein turnover or the antiproteolytic response to moderate inte nsity exercise or weight loss. We conclude that the previously observe d defect in insulin suppression of leucine flux in upper body obese wo men appears related to insulin resistance and does not represent an in herent abnormality of protein metabolism.