Low-Carbohydrate Versus Low-Fat Diets

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Stern L, Iqbal N, Seshadri P, et al.: The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: One year follow-up of a randomized trial. Ann Intern Med 140:778-785, 2004.

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

In the past, for weight loss, doctors have recommended a diet high in complex carbohydrates (like whole grain breads and cereals) and low in fat and calories.

Low-carbohydrate diets are now very popular. Researchers did an earlier study of obese patients on a low-carbohydrate diet or a low-fat diet. After six months, those on the low-carbohydrate diet lowered the levels of fat in their blood and had better blood glucose control.

Why did the researchers do this particular study?

The researchers also wanted to know if the results for those in the six-month study were the same for a one-year study after the patients began the diets.

Who was studied?

A total of 132 people 18 and older were studied between May and November 2001.

How was the study done?

Sixty-four people followed the low-carbohydrate diet; the others followed a low-fat diet. The groups met weekly for four weeks, then once a month for 11 months. The low-carbohydrate group reduced their carbohydrates to less than 30 grams each day. The low-fat group reduced their calorie totals by 500 each day.

The researchers checked weight, medical history, blood pressure, fasting blood glucose, and cholesterol measurements.

What did the researchers find?

The low-carbohydrate group reduced their calorie intake more than those in the low-fat group. Those in the low-carbohydrate group stayed around the same weight in both the short-term and long-term follow-up. The low-fat group continued to lose weight in the long-term follow-up. The total amount of weight lost between the two groups, however, was about the same.

What were the limitations of the study?

Many participants dropped out of the study. Another problem was that most people did not reach the dietary goals set by the researchers. Had more people stayed in the study and reached their goals, the results might have been different.

What are the implications of the study?

The researchers found similar weight loss in both diet groups. The low-carbohydrate group decreased fats in the blood quicker and had better blood glucose control. An important study might be how low-carbohydrate diets affect the development of diabetes and heart disease.