The prevalence of impaired glucose tolerance (IGT) increases with aging. Although some data suggest that age is independently associated with IGT, other studies suggest that age-associated changes in body composition and reduced cardiovascular fitness are responsible for the development of IGT. We, therefore, examined the relationship of age, total and regional adiposity, and level of fitness (VO2max) to the presence of IGT in 155 healthy, nondiabetic, nonsmoking, older community dwelling men. Sixty-two of 155 men (40%) had IGT, while 93 men (60%) had normal glucose tolerance (WHO criteria). The subjects with IGT were of similar age (61.0 +/- 1.0 vs. 59.0 +/- 0.7 years, p = 0.49) and had the same maximal aerobic capacity, (VO2max) (42.0 +/- 1.0 vs. 44.0 +/- 0.8 mL/kg ffm/min, p = 0.42), but had a higher waist to hip ratio (WHR) (0.98 +/- 0.01 vs. 0.96 +/- 0.01, p = 0.005) and percent body fat (30.0 +/- 0.4 vs. 26.0 +/- 0.6, p = 0.004) than the men with normal glucose tolerance. In univariate analysis, the 2-h glucose level correlated positively with percent body fat (r = 0.30, p = 0.0002), WHR (0.24, p = 0.002), and age (r = 0.17, p = 0.03) and negatively with VO2max (r = -0.23, p = 0.005). In both multiple logistic and linear regression analyses, percent body fat was the only independent predictor of IGT (p = 0.002). These results suggest that the age-associated increase in total adiposity is a major contributor to the development of IGT in middle-aged and older men. Thus, lifestyle modifications that reduce body fat should reduce the risk for IGT and the development of noninsulin-dependent diabetes mellitus in the elderly.