Several recent clinical studies show that a low-carbohydrate diet produces a greater initial weight loss than conventional low-fat diets, and is associated with a greater reduction of elevated serum triglycerides. After one year, however, weight loss is similar with both diets. Since the intake of saturated fat is higher on a low-carbohydrate diet, there may be an increased risk of elevated levels of LDL cholesterol, thus furthering atherosclerosis, over the long term. Before low-carbohydrate diets can be considered an equivalent alternative to low-fat diets for the treatment of obesity, long-term clinical trials are urgently required. The greater weight loss under low-carbohydrate diets would appear to be due to a lower caloric intake. Successful weight loss largely depends on restricting the intake of calories, but the supply of essential nutrients should be guaranteed.