BODY FATNESS AND WAIST CIRCUMFERENCE ARE INDEPENDENT PREDICTORS OF THE AGE-ASSOCIATED INCREASE IN FASTING INSULIN LEVELS IN HEALTHY-MEN ANDWOMEN

OBJECTIVE: Elevated levels of fasting insulin increase the risk for co ronary artery disease. In this study, we considered the independent co ntributions of age, total body fatness, abdominal fat distribution, pe ak aerobic capacity, leisure time physical activity, dietary intake, a nd fasting glucose levels to the age-associated increase in fasting in sulin levels in healthy men and women. DESIGN: A cross-sectional analy sis. SUBJECTS: A total of 427 healthy men and 293 healthy women age 18 to 90 years.MEASUREMENTS: Plasma glucose and insulin levels were meas ured in the fasted state and subjects were characterized for body fatn ess from underwater weighing, abdominal fat distribution from the wais t circumference, peak VO2 from a treadmill test to exhaustion, leisure time physical activity from a structured interview and dietary intake from a 3-day food diary. The independent predictors of fasting insuli n levels were determined by stepwise multiple regression analysis. RES ULTS: Pasting insulin concentrations increased with age in both men (0 .09 +/- 0.02 pmol/yr, unadjusted slope +/- SEE) and women (0.14 +/- 0. 03 pmol/yr). In men, the major independent predictors of fasting insul in levels were percent body fat (r(2) = 28%, P < 0.001) and waist circ umference (r(2) = 3% P < 0.001). Age, glucose concentration,and peak V O, were small (1% each), but independent contributors to the variance in insulin levels. In women, the waist circumference (r(2) = 18%, P < 0.001) and the fasting glucose concentration (r(2) = 7%, P < 0.001) we re the independent correlates of fasting insulin concentrations. CONCL USIONS: Our data suggest that total adiposity and central body fat dis tribution are significant determinants of the increase in fasting insu lin levels, whereas age, dietary intake, and levels of aerobic fitness and physical activity appear to be less important contributors to the variation in fasting insulin concentrations in healthy men and women.