Diet and Syndrome X.

Syndrome X is a cluster of abnormalities, associated with resistance to insulin-mediated glucose uptake, that increases risk of coronary heart disease. Increased carbohydrate intake (with reciprocal decreased fat intake) within the boundaries of menus that can be followed in the free-living state have not been shown to decrease insulin resistance directly, by enhancing insulin sensitivity, or indirectly, by producing and maintaining weight loss. Moreover, such diets accentuate the metabolic abnormalities that constitute Syndrome X. Substitution of monounsaturated fat, polyunsaturated fat, or both for saturated fat results in the same reduction in low-density lipoprotein-cholesterol concentration as seen in diets low in fat and high in carbohydrates but without any untoward effects on the various manifestations of Syndrome X. Consequently, substituting unsaturated fat for saturated fat, without increasing intake of dietary protein or carbohydrate, may be useful for patients with hypercholesterolemia, Syndrome X, or both.