Comparing Very Low-Carbohydrate and Low-Fat Diets

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Volek JS, Sharman MJ, Gómez AL, et al.: Comparison of very low-carbohydrate and low-fat diet on fasting lipids, LDL subclasses, insulin resistance, and postprandial lipemic response in overweight women. J Am Coll Nutr 23:177-184, 2004.

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

Many popular diets claim that people will lose more weight if they eat a low-carbohydrate diet (which include foods like crackers, bread, and pasta). Other diets claim that reducing the amount of calories is the key to losing weight. Several studies have found that low-carbohydrate diets result in greater weight loss than low-fat diets.

Few studies, however, have looked at the effects of very low-carbohydrate diets on high blood fats people have after meals. The amount of fat in your blood relates to how healthy your heart is. The researchers in this study wanted to find out if a low-calorie diet or a low-carbohydrate diet was better for a healthy heart.

Who was studied?

Thirteen overweight and obese women participated in the study. None of the women were on special diets or were smokers. All ate between 27% and 41% of their calories from fat before the study. The women did little or no exercise.

How was the study done?

The women went on two weight-loss diets for 4 weeks each. One diet was low fat; the other was a very low-carbohydrate diet. All participants received instructions and guidance at the beginning of the study and had follow-up meetings with registered dietitians.

The very low-carbohydrate diet included beef, fish, oils, nuts and seeds, peanut butter, some vegetables, salads with low-carbohydrate dressing, some cheese, eggs, protein powder, and water or low-carbohydrate diet drinks.

Fasting blood samples (taken before they ate) were taken two days before each 4-week diet plan. Blood fats, glucose, and insulin also were tested.

What did the researchers find?

The women lost much more weight on the very low-carbohydrate diet than on the low-fat diet.

The women's cholesterol (measured before they ate) was lower in the low-fat diet.

The women's glucose (measured before they ate), insulin, and insulin resistance levels were lower after the very low-carbohydrate diet.

What were the limitations of the study?

Because the study was short, it is difficult to know if the same results would be achieved if the study was done over a longer period of time. Also, there were only 13 people in the study.

What are the implications of the study?

The results of this study show that short-term, low-fat and very low-carbohydrate diets can help people lose weight and reduce the amount of fats in their blood after a meal. Further studies should be done to find out if the long-term results are the same as the short-term results.