Reversibility of chronic experimental syndrome X by diet modification.

This study was designed to examine whether abnormalities that comprise the metabolic syndrome, including insulin resistance, hyperinsulinemia, hypertension, hyperlipidemia, and obesity, are reversible by diet. Female Fischer rats were placed on either a high-fat, refined-carbohydrate (HFS) diet or low-fat, complex-carbohydrate (LFCC) diet for a period of 20 months. After 20 months, a group of HFS rats were switched to the LFCC diet (HFS/LFCC) for a period of 2 months. Skeletal muscle glucose transport, plasma insulin, systolic blood pressure, and plasma lipids were measured in all groups after 22 months. Energy intake and body weight were measured weekly. In the HFS group, insulin-stimulated glucose transport was significantly reduced (67+/-4 versus 98+/-4 pmol. mg(-)(1). 15 s(-)(1)), whereas plasma insulin (300+/-49 versus 82+/-8 pmol/L), blood pressure (147+/-4 versus 123+/-4 mm Hg), plasma triglycerides (2.58+/-0.31 versus 0.39+/-0.04 mmol/L), LDL cholesterol (C) (3.45+/-0.40 versus 0.89+/-0.06 mmol/L), LDL-C to HDL-C ratio (2.9+/-0.1 versus 2.2+/-0.1), VLDL-C (1.53+/-0.23 versus 0.37+/-0.07 mmol/l), Total-C (5.56+/-0.58 versus 1.49+/-0.10 mmol/L), and body weight (360+/-11 versus 260+/-5 g) were all significantly elevated compared with the LFCC. Energy intake did not differ significantly; however, the LFCC had a much poorer feed efficiency. Conversion to a LFCC diet for 2 months led to normalization of glucose transport, blood pressure, plasma insulin, and VLDL-C and significant amelioration of obesity and other lipid abnormalities. These results demonstrate that syndrome X induced by an inappropriate diet is reversed with implementation of a low-fat, unrefined-carbohydrate diet without caloric restriction and suggest that diet may be a possible treatment for multiple simultaneous cardiovascular risk factors.

Do high carbohydrate diets prevent the development or attenuate the manifestations (or both) of syndrome X? A viewpoint strongly against.

Syndrome X refers to a cluster of abnormalities, associated with resistance to insulin-mediated glucose uptake that increase risk of coronary heart disease. Increases in carbohydrate intake (with reciprocal decreases in fat content) within the boundaries of menus that can be followed in the free-living state have not been shown to decrease insulin resistance, either directly by enhancing insulin sensitivity or indirectly by producing and maintaining weight loss. However, such diets accentuate the metabolic abnormalities that constitute syndrome X. Because substitution of monounsaturated or polyunsaturated fat, or both, for saturated fat results in the same fall in LDL-cholesterol concentration as seen with low fat/high carbohydrate diets, it is concluded that low fat/high carbohydrate diets should be avoided in the treatment of syndrome X.