Age-related differences in body fat and more specifically in the accumulation of abdominal visceral adipose tissue were examined as a potential covariate for the alteration in the plasma lipoprotein profile found with aging. For that purpose, results from 79 young adults (aged 24.5 +/- 4.0 years) were compared to 61 middle-aged men (54.7 +/- 6.4 years). Younger men had significantly lower body fat mass and abdominal visceral adipose tissue area measured by computed tomography than middle-aged men (P < 0.0001). Plasma cholesterol, triglyceride, apolipoprotein (apo) B, low density lipoprotein (LDL)-cholesterol and LDL apo B levels, as well as the ratio of plasma cholesterol to high density lipoprotein (HDL)-cholesterol were all significantly lower in younger men as compared to middle-aged men (P < 0.0001). The comparison of younger men to middle-aged men with comparable levels of abdominal visceral fat and total body fat eliminated the age-related differences in plasma triglyceride and in the ratio of plasma cholesterol to HDL-cholesterol, whereas the difference in plasma apolipoprotein B levels, although still significant, was largely reduced. Age-related differences in plasma cholesterol and in LDL-cholesterol levels were still observed after this matching procedure and the differences between age-groups were essentially of similar magnitude than before pairing. In summary, these results suggest that the deterioration of plasma lipoprotein profile observed in middle-aged men as compared to young adult men is partly mediated by concomitant increases in total body fat and abdominal visceral adipose tissue. However, other factors related to the aging process appear to be involved, particularly for the age-related increase in plasma LDL-cholesterol.