Low-Carb Diets - Does Science Support Them?

Although high-protein diets have been extremely popular, many health experts have questioned their safety and efficacy. However, over the past year, several studies have been published regarding high-protein diets, with some interesting results.

Researchers, led by Gary Foster, clinical director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine, West Philadelphia, evaluated high-protein diets versus other diet programs. In this first study, researchers randomly assigned both obese men and women to either the Atkins diet (low-carb) or a low-calorie, high-carbohydrate diet. After a six-month period, participants on the Atkins diet lost 15 pounds, whereas those on the more conventional diet lost 7 pounds. However, after one year, both groups had kept off approximately the same amount of weight.

In another study, researchers from the Philadelphia Veterans Affairs Medical Center followed severely obese men and women on either a low-carbohydrate diet similar to the Atkins plan, or a low-fat plan. After six months, the low-carbohydrate followers lost 13 pounds, whereas the low-fat dieters lost 4 pounds. (Weight loss after one year was not reported.) The findings of the two studies were published in the New England Journal of Medicine.

Another study, which compared an American Heart Association (AHA)-type diet with a low-carbohydrate diet found that participants were able to lose weight as well as lower their cholesterol levels on the low-carbohydrate plan. The findings were presented at the AHA meeting in November 2002. However, the AHA issued the following concerns regarding the study:

· The study evaluated a very small group with only 120 total participants -- only 60 consumed the high-fat, low-carbohydrate diet.

· This was a short-term study over a period of just six months. The conclusions from the study did not indicate that the weight loss could be maintained over the long-term.

· The conclusions from the study did not provide evidence over the long-term that such a diet could be beneficial in improving long-term health.

· The diet was not conducted over a time period long enough to evaluate the risk of heart disease. A diet high in saturated fat contributes to heart disease.

· A direct comparison (between dietary recommendations from the AHA and the Atkins diet) was not studied.

Finally, a recent review of medical studies (from approximately 40 years ago to the present) has found that cutting carbohydrates from the diet is not always effective. Dena Bravata, M.D., M.S., of the Stanford University School of Medicine in Palo Alto, CA, and her team of researchers conducted the review, which was published in the Journal of the American Medical Association. The researchers evaluated dietary studies published between 1966 and 2003 to determine how low-carbohydrate diets affected weight, cholesterol, glucose, insulin levels and blood pressure. The results indicated that among obese patients, the amount of weight loss was linked to compliance to the diet, not how many carbohydrates were cut. The research team also pointed out that only five of the studies lasted longer than 90 days, so the long-term effects of restricting carbohydrates is not well understood.

Most experts agree that these findings do offer some insight into the effectiveness of low-carbohydrate diets, but the jury is still out. Many questions remain unanswered and more research is needed before such diets can be recommended for weight loss, weight maintenance and overall health.

Reprinted with permission from the Calorie Control Council's Fall 2003 "Calorie Control Commentary," newsletter www.caloriecontrol.org/commentary_f03.pd. Beth Hubrich, M.S., R.D., L.D., serves as Associate Director of the Calorie Control Council. The Calorie Control Council, established in 1966, is an international nonprofit association representing the low-calorie and reduced-fat food and beverage industry. Today, it represents 60 manufacturers and suppliers of low-calorie, low-fat and light foods and beverages, including the manufacturers and suppliers of more than a dozen different dietary sweeteners, fat replacers and other low-calorie ingredients. For more information, please visit www.caloriecontrol.org or www.cccbiz.org.

Back to top