Low-carbohydrate diets are increasingly popular, but concerns have arisen that such diets, compared with traditional low-fat diets, might have adverse cardiovascular (CV) consequences. To evaluate the effects of both diets on weight and CV risk factors, U.S. researchers randomized 148 adults (mean age, 47; mean body-mass index, 35 kg/m2; 51% black; none with CV disease or diabetes) to either a diet that limited carbohydrates to <40 g daily or a diet in which <30% of daily energy intake came from fats (<7% from saturated fat). Participants met regularly with dieticians and were followed for 1 year; no caloric intake goals were given, and participants were asked not to change their physical activity levels.

During the trial, total energy intake was slightly lower in the low-carbohydrate group than in the low-fat group (e.g., 1324 vs. 1481 kcal daily at 6 months); physical activity levels were similar in both groups. At 12 months, mean weight reduction was significantly greater in the low-carbohydrate group than in the low-fat group (difference, −3.5 kg), as were mean decreases in triglyceride levels (difference, −14.1 mg/dL) and mean increases in HDL cholesterol levels (difference, 7.0 mg/dL). Levels of total and LDL cholesterol did not change significantly in either group, nor did blood pressure or plasma glucose levels. Ten-year Framingham risk scores were significantly lower in the low-carbohydrate group (mean difference, −1.4%).

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