EXERCISE BLUNTS DECLINES IN LIPOLYSIS AND FAT OXIDATION AFTER DIETARY-INDUCED WEIGHT-LOSS IN OBESE OLDER WOMEN

Weight loss (WL) by hypocaloric diet decreases adipocyte lipolysis and fat oxidation, adaptations that might predispose individuals to regai n weight. Our hypothesis was that the addition of endurance exercise ( EX) to dietary-induced WL (6 mo; 250-350 kcal/day deficit) would preve nt declines in abdominal (ABD) and gluteal (GLT) adipocyte lipolysis a nd fat oxidation in obese older women. At baseline, the WL(n = 9) and WL+EX(n = 11) groups had similar body composition, fat distribution, a erobic fitness ((V)over dot O-2 max), and resting fat metabolism. Redu ctions in body weight (WL = 11%, WL+EX = 8%), percent body fat, and in tra-abdominal fat area with the interventions were similar in both gro ups, but (V)over dot O-2 increased (9%, P < 0.01) only in the WL+EX gr oup. Basal and adrenergic receptor- and postreceptor-stimulated lipoly sis in ABD and GLT adipocytes decreased (20-70%, P < 0.05) in the WL g roup but did not change in the WL+EX group. Fat oxidation decreased (3 8%, P < 0.05) in the WL group but not in the WL+EX group. The changes in fat oxidation and GLT lipolysis differed significantly between grou ps. Fat oxidation correlated positively with ABD and GLT adipocyte bas al lipolysis at baseline (r = 0.45 and r = 0.53, P < 0.05), and the ch anges in fat oxidation with the interventions correlated positively wi th changes in ABD and GLT adipocyte basal lipolysis (r = 0.50 and r = 0.42, P < 0.05) in the entire group of women. These results indicate t hat exercise counteracts the decline in fat oxidation with WL, in part by maintaining adipocyte lipolytic responsiveness in some weight-redu ced postmenopausal women.