Low-Carbohydrate Diet Shows More Weight Loss Than Low-Fat Diet

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Yancy WS, Olsen MK, Guyton JR, et al.: A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia. Ann Intern Med 140:769-777, 2004.

What is the problem and what is known about it so far?

Low-carbohydrate diets are very popular, but there isn't much research on their effectiveness.

Why did the researchers do this particular study?

The researchers wanted to compare a low-carbohydrate diet with a low-fat, low-cholesterol (fats in the blood), reduced-calorie diet.

Who was studied?

Included in the study were 120 overweight people with high levels of fat in their blood. They were between 18 and 65 years old and otherwise in good health.

How was the study done?

Participants were put into two groups: one followed a low-carbohydrate diet, and the other followed a low-fat, reduced-calorie diet. Participants attended group meetings twice each month for 3 months, then monthly for 3 months. At meetings, participants received diet information and were weighed. Everyone was encouraged to exercise for 30 minutes three times each week.

The low-carbohydrate diet group was to eat fewer than 20 grams of carbohydrate daily. When a member was halfway to weight-loss goal, he or she added 5 grams of carbohydrate to the daily diet.

The low-fat diet group was to eat less than 30% fat and fewer than 300 milligrams of cholesterol daily. Depending on their weight, people in this group were to eat 500 to 1,000 fewer calories per day.

What did the researchers find?

During the 24-week study, researchers found that the low-carbohydrate group lost more weight and reduced blood fat levels more than the low-fat group.

What were the limitations of the study?

More people in the low-fat group dropped out of the program than in the low-carbohydrate group; this could have an affect on the study's results.

The study lasted 6 months, so it is hard to know the long-term results. Also, only healthy volunteers were used; results may be different in people with medical conditions.

What are the implications of the study?

Although this study showed that the low-carbohydrate diet group lost more body weight and fat than those in the low-fat diet, more studies are needed to understand the effects of a low-carbohydrate diet for longer periods of time.