The prevalence of obesity in the United States has doubled in the past 20 years and is rapidly becoming one of our largest public health problems. Indeed, at any given time, as many as 45% of all American women and 30% of all American men are trying to lose weight, many of them with limited or no success.

At the heart of these efforts lies the conventional high-carbohydrate, low-fat, low-calorie diet, an approach that, in the face of this lack of success, has lost popularity in recent years. However, alternatives to this conventional approach inspire sometime heated controversy, particularly the low-carbohydrate, high-protein, high-fat (Atkins) diet.

Recently, a group of researchers attempted to determine whether or not the popular low-carbohydrate diet was truly more effective for weight loss than the more conventional approach. This study, published in the May 22, 2003 issue of the New England Journal of Medicine , found that the low-carbohydrate diet produced a greater weight loss than the conventional diet for the first six months, but the differences were not significant at one year.

About the study

The researchers conducted a one-year, multicenter, controlled trial involving 63 obese men and women who were randomly assigned to either a low-carbohydrate, high-protein, high-fat diet or a low-calorie, high-carbohydrate, low-fat (conventional) diet.

Participants on the low-carbohydrate diet were instructed to limit their intake of carbohydrates to 20 grams per day for the first two weeks of the diet, and then gradually increase their carbohydrate consumption until a stable desired weight was achieved. No restrictions were placed on their consumption of protein or fat. They were also given a copy of “Dr. Atkins New Diet Revolution” and instructed to read it and follow the diet as described in the book.

Participants on the conventional diet were instructed to follow a high-carbohydrate, low-fat, low-calorie diet (women 1200-1500 calories per day; men 1500-1800 calories per day), with approximately 60% of their calories from carbohydrates, 25% from fat, and 15% from protein. These participants were given a copy of “The LEARN (lifestyle, exercise, attitudes, relationships, nutrition) Program for Weight Management” and asked to read it and follow the program as described.

The findings

The researchers found that the participants who followed the low-carbohydrate diet had lost significantly more weight at 3 and 6 months than had those following the conventional low-calorie diet. However, this difference was no longer significant by one year.

The researchers also found that the low-carbohydrate diet was associated both increased levels of HDL (good) cholesterol and decreased levels of triglycerides.

How does this affect you?

The results of this study demonstrate that the low-carbohydrate, high-fat, high-protein Atkins diet produced greater weight loss than a conventional diet for up to six months, but that this difference was not maintained for one year. This is likely due to greater weight re-gain by those participants who followed the low-carbohydrate diet and may reflect the difficulty of adhering to this type of diet over the long term. Also, one important unanswered question is the effect of limited carbohydrates and abundant fats on the risk of coronary heart disease over time. It is true that in this study, the participants on the low-carbohydrate diet demonstrated a greater improvement in some risk factors for coronary heart disease , however, the researchers recommend that longer, larger studies be conducted to determine the long-term safety and efficacy of the low-carbohydrate diet.

A second study published in the same issue of the New England Journal of Medicine , found that a small group of severely obese patients, all of whom were either diabetic or showed evidence of the metabolic syndrome (elevated blood sugar, insulin and triglyceride levels), lost more weight over six months on a low-carbohydrate diet than on a conventional diet. This same group of patients also showed increases in insulin sensitivity and decreases in their triglyceride levels. The researchers warn, however, that these findings should be viewed with caution until larger, longer studies have been conducted.

While neither of these studies settles the debate, they certainly offer important insights into the issue. In the end, there was little to no difference in the amount of weight lost by the participants after one year, regardless of the diet plan they followed. This result seems more a testament to the difficulty of achieving long-term, permanent weight loss than an endorsement or condemnation of either diet approach. Despite our relentless search for a magic bullet, it seems our battle with obesity rages on.