DISTINCT EFFECTS OF AEROBIC EXERCISE TRAINING AND WEIGHT-LOSS ON GLUCOSE-HOMEOSTASIS IN OBESE SEDENTARY MEN

The decline in glucose homeostasis with aging mag be due to the physic al deconditioning and obesity that often develop with aging. The indep endent and combined effects of aerobic exercise training (AEX) and wei ght loss (WL) on glucose metabolism were studied in 47 nondiabetic sed entary older men. There mere 14 men in a weekly behavioral modificatio n/WL program, 10 in a 3 times/wk AEX program, 14 in an AEX + WL progra m, and 9 in the control (Con) group. The 10-mo intervention increased maximal oxygen consumption (VO2max) in both the AEX and AEX+WL groups [0.33 +/- 0.05 and 0.37 +/- 0.09 (SE) l/min, respectively], but VO2max did not significantly change in the WL(0.01 +/- 0.06 l/min) and Con g roups (-0.04 +/- 0.05 l/min, P > 0.05. The AEX;WL and WL groups had co mparable reductions in body weight (-8.5 +/- 0.9 and -8.8 +/- 1.2 kg, respectively) and percent fat (-5.5 +/- 0.7 and -5.9 +/- 1.1%, respect ively) that were significantly greater than those in tile Con and AEX groups. Oral glucose tolerance tests shaved significant reductions in insulin responses in the AEX, WL, and AEX + WL groups, but tile decrea se in insulin response in the AEX + WL group was significantly greater than that in tile other three groups. The glucose area decreased sign ificantly in the WL and AEX + WL groups but did not change in the Con or AEX groups. There were significant increases in insulin-mediated gl ucose disposal rates as measured by the hyperinsulinemic (600 pmol . m (-2). min(-1)) euglycemic clamps in the AEX and AEX+WL groups [1.66 +/ - 0.50 and 1.76 +/- 0.41 mg kg fat-free mass (FFM)(-1). min(-1), respe ctively] that were significantly greater than those in the WL(0.13 +/- 0.31 mg . kg FFI-1.-min(-1)) and Con groups (-0.05 +/- 0.51 mg . kg F FM(-1). min(-1); n = 5). These data suggest that AEX and WL improve gl ucose metabolism through different mechanisms and that the combined in tervention of AEX + WL is necessary to improve both glucose tolerance and insulin sensitivity in older men.