Studies employing analysis of
LDL subclasses have demonstrated heterogeneity of the
LDL response to low fat, high
carbohydrate diets in healthy nonobese subjects. In individuals with a genetically influenced atherogenic
lipoprotein phenotype, characterized by a predominance of small dense
LDL (
LDL subclass pattern B), lowering of plasma
LDL cholesterol levels by diets with < or =24% fat has been found to represent a reduction in numbers of circulating mid-sized and small
LDL particles, and hence an expected lowering of
cardiovascular disease risk. In contrast, in the majority of healthy individuals with larger
LDL (pattern A, found in approximately 70% of men and a larger percentage of women), a significant proportion of the
low fat diet-induced reduction in plasma
LDL cholesterol is made by depletion of the
cholesterol content of
LDL particles. This change in
LDL composition is accompanied by a shift from larger to smaller
LDL particle diameters. Moreover, with progressive reduction of
dietary fat and isocaloric substitution of
carbohydrate, an increasing number of subjects with pattern A convert to the pattern B phenotype. Studies in families have indicated that susceptibility to induction of pattern B by
low fat diets is under genetic influence. Thus, diet-gene interactions affecting
LDL subclass patterns may contribute to substantial interindividual variability in the effects of
low fat diets on
coronary heart disease risk.