Effect of the amount of body fat on the age-associated increase in serum cholesterol

This study investigates the contribution of body fat stores on the age-associated increase in serum cholesterol and triglyceride levels. Percentage of body fat was measured by hydrostatic weighing, and serum cholesterol, triglyceride, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels were determined in a sample of 472 healthy men and women ages 18–50 years. In both sexes, body fat mass was significantly correlated with serum cholesterol (r = 0.21 in men and r = 0.24 in women, P < 0.01) and triglyceride (r = 0.33 in men and r = 0.24 in women, P < 0.01) levels. After adjustment for the association between age and serum cholesterol, no correlation was observed between body fat mass and serum cholesterol (r = 0.01 in men and r = 0.09 in women). After correction for age, serum triglyceride levels remained significantly correlated with body fat mass (r = 0.26 and r = 0.17 in men and women, respectively, P < 0.05). As body fat also increases with age, the possibility that a partial correlation coefficient procedure eliminated a portion of the age effect mediated by an age-related increase in fat, was addressed by performing further analyses. Within each sex subsample two sets of analyses were performed on (a) three groups of subjects individually paired for age but with different levels of body fat stores, and (b) three groups of subjects paired for the amount of body fat but differing in age. When subjects were paired for age, analysis of variance revealed a significant effect of increased body fat stores on serum triglyceride (P < 0.01 in men and P < 0.05 in women) but no effect on serum cholesterol and low-density lipoprotein cholesterol levels. However, when groups were paired for percentage body fat, a significant effect of age on serum cholesterol and low-density lipoprotein cholesterol was observed in men (P < 0.05 and P < 0.01) and in women (P < 0.01). These results suggest that factors other than the increase in adipose tissue stores are responsible for the increases in serum cholesterol and low-density lipoprotein cholesterol levels observed with age.