SERUM LEPTIN LEVELS ARE REDUCED IN RESPONSE TO EXERCISE TRAINING, BUTNOT HORMONE REPLACEMENT THERAPY, IN OLDER WOMEN

The aim of this study was to evaluate the effects of exercise training and hormone replacement therapy (HRT) on serum leptin levels in older women. Previously sedentary, healthy women, aged 60-72 yr, were assig ned to control (n = 16), exercise (n = 17), HRT (n = 15), or exercise + HRT (n = 13) groups. Exercise training consisted of a 2-month flexib ility-exercise program followed by a 9-month exercise program that inc luded walking, jogging, and stair climbing. HRT consisted of 11 months of continuous conjugated estrogens (0.625 mg/day) and medroxyprogeste rone acetate (5 mg/day) for 13 days every third month. Body compositio n was assessed by dual-energy x-ray absorptiometry, and serum insulin levels were measured in the fasted state and in response to a glucose challenge. Leptin levels were reduced by 23 +/- 25% and 22 +/- 27% (bo th P < 0.01) in response to exercise and exercise + HRT, respectively. There was no effect of HRT on leptin. Fat mass was the strongest pred ictor of serum leptin concentration, both before (r = 0.81; P < 0.001) and after (r = 0.85; P < 0.001) the study period, and the change in f at mass in the exercisers was significantly correlated with the change in leptin (r = 0.55; P < 0.01). There did not seem to be an effect of exercise, independent of the reduction in fat mass, on leptin. Insuli n levels were significantly correlated with leptin levels, but this wa s not independent of the association with adiposity. The curvilinear r elationship between leptin level and fat mass and the finding that the ratio of leptin mass to fat mass decreased after weight loss suggest that fat cell size is an important determinant of circulating leptin l evels.