INFLUENCE OF GENDER, BODY-MASS INDEX, AND AGE ON RESPONSE OF PLASMA-LIPIDS TO DIETARY-FAT PLUS CHOLESTEROL

We have conducted a crossover, randomized, double-blind dietary trial that tested the hypothesis that gender influences the response of plasma lipids, in particular high density lipoprotein (HDL) cholesterol, to dietary fat plus cholesterol. Twenty-six men and 25 women were matched for age, low density lipoprotein (LDL) cholesterol, triglyceride, and body mass index (BMI). After a 2-week baseline low-fat (27% of calories), low-cholesterol period, subjects were given two isocaloric liquid supplements for 3 weeks each, one containing 31 g fat (56% saturated) and 650 mg cholesterol, and the other fat free. The baseline HDL2 cholesterol level was significantly higher in women: 0.41 versus 0.26 mmol/l (p<0.01). Importantly, women also showed a greater rise in HDL2 cholesterol concentration with the fat/cholesterol supplement: 0.09 versus 0.03 mmol/l (p<0.01). The greater increment in women was related to their higher baseline HDL2 cholesterol levels. With the fat and cholesterol supplement, LDL cholesterol values rose from 3.76 to 4.04 mmol/l in women and from 3.77 to 4.13 mmol/l in men. The baseline LDL cholesterol value was found to account for about 35% of the variance in the rise in LDL cholesterol level with fat and cholesterol supplementation in both men and women <50 years. In men only, there was a significant effect of age: the change in LDL cholesterol with the fat/cholesterol supplement was 0.16 mmol/l in those <50 and 0.54 mmol/l in those >50 years old (p<0.01). Only hypercholesterolemic men and women responded with significant increases in LDL and HDL3 cholesterol; subjects with initial plasma cholesterol levels <5.5 mmol/l showed either no change or a rise in HDL2 Cholesterol level. Men with a BMI >25 kg/m2 experienced no rise in HDL2 cholesterol, whereas women with a similar degree of obesity showed a rise in HDL2 cholesterol level that was no different from that seen in nonobese women. Thus, men and women differ significantly in their response to dietary fat and cholesterol: women respond with a greater rise in HDL2, whereas men, especially older men, transport excess cholesterol preferentially in LDL. These findings were highly repeatable; when 15 subjects were retested after 6 months, the responses on the two occasions were significantly correlated (r=0.63, p<0.01).