Low-carbohydrate diets have become popular in the past few decades, with the Atkins diet being the most popular. The Atkins diet is a high-protein and/or high-fat, a very-low-carbohydrate diet that induces ketosis. The very ̶ low-carbohydrate content is critical in inducing short-term weight loss in the first 2-4 weeks; this is largely the result of fluid mobilization.

Ketone bodies tend to be generated when an individual’s daily dietary carbohydrate intake is under 50g, and sodium diuresis is forced, causing most of the short-term weight loss. No robust data on the safety or long-term effectiveness of this diet are available.

The premise of the diet is that caloric intake as protein is less prone to fat storage than is the equivalent caloric intake as carbohydrate; however, no physiologic data support this premise. Owing to the high-fat content of such diets, low-density lipoprotein cholesterol (LDL-C) levels were found to be increased by at least 10% in 25% of patients who used this diet.

Data on the long-term effects of a high-protein diet in rodents cause concern. They indicate that these diets may be associated with a reduced life span and a predisposition to neoplasia.

In 2 randomized trials, weight loss with Atkins-type diets was compared with conventional low-fat or balanced calorie-deficit diets.

Although the Atkins-type diet led to the greatest initial weight loss, weight loss became similar within 1 year. Adherence to this diet is poor; in those studies noted, the noncompliance rate in the Atkins-type group was close to 50%.

The South Beach diet is another low-carbohydrate diet. This program is more liberal in its carbohydrate allowance than the Atkins diet. In addition, the South Beach diet distinguishes between what is considered to be good and bad carbohydrates on the basis of their glycemic index.

Although the relevance and importance of the glycemic index are controversial, the diet encourages increased fiber intake, which is associated with lowered weight even when total caloric intake is relatively unchanged. Low glycemic index diets are better at helping to maintain weight loss than diets with a higher glycemic index; the same is true for diets with modestly increased protein intake, versus standard protein intake.

Persons who decide to use a low-carbohydrate diet should choose heart-healthy sources of fat, including monounsaturated fats, polyunsaturated fats, and fats rich in omega 3 fatty acids, rather than saturated fat. Protein sources should be fish, nuts, legumes, and lean poultry rather than pork chops, steak, and mutton.