CONTRIBUTION OF VISCERAL FAT MASS TO THE INSULIN-RESISTANCE OF AGING

Recent studies have shown that central obesity (increased waist to hip ratio [WHR]) is related to insulin resistance and aging. Furthermore, in central obesity states, the intraabdominal fat (IAF) depot has been postulated to contribute most to the development of insulin resistance. Therefore, the observed insulin resistance of aging may be related more to changes in body composition than to aging per se. The purpose of this study was to explore the association of IAF with age and insulin sensitivity (S-I) after controlling for obesity. We examined 60 healthy nondiabetic subjects (normal 75-g oral glucose tolerance test, aged 23 to 83, 15 men and 45 women). We chose subjects so that those less than or equal to 125% and greater than 125% of ideal body weight were equally represented in each age decade. We quantified total and subcutaneous abdominal fat and IAF at the umbilicus using a validated magnetic resonance imaging (MRI) scanning technique and determined S-I using a modified minimal model. IAF correlated significantly with age (r = .49, P = .0001) in the group as a whole, as well as in men (r = .58, P = .022) and women (r = .48, P = .0008) separately. In all subjects, S-I was significantly related to IAF (r = -.50, P < .0001) but was not related to age (r = .00, P = .98). In multivariate analysis for various combinations of age, sex, and measures of fat distribution, WHR accounted for 28% and IAF for 51% of the variance in S-I, whereas age, sex, and interactions of age and sex accounted for only 1%. In conclusion, IAF mass, which has been postulated to be the most metabolically active of the adipose depots, correlates significantly with insulin resistance and age in healthy nondiabetic individuals regardless of gender and after controlling for obesity. Copyright (C) 1995 by W.B. Saunders Company