Low-carb diets appear to have a positive effect on weight loss

16/02/06 A synthesis of data from five previous clinical trials suggests that both low-fat and low-carbohydrate diets appear to be effective for weight loss up to one year, but low-carbohydrate diets may be linked to higher overall and LDL or “bad” cholesterol levels, according to a study in the February 13 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

As obesity levels increase, more American adults are dieting—at any one time, 45 percent of women and 30 percent of men are trying to lose weight, according to background information in the article. Those who succeed may reduce their risk of type 2 diabetes, control their hypertension and decrease their chances of cardiovascular disease and related death. Low-carbohydrate, high-protein diets have become a popular alternative to the generally recommended low-fat, calorie-restricted diet, the authors report. However, because these diets contain large amounts of protein and fat, concern remains about their effect on cholesterol levels and the cardiovascular system, they write.

Alain J. Nordmann, M.D., M.Sc., University Hospital Basel, Switzerland, and colleagues analyzed five previous clinical trials that compared low-fat to low-carbohydrate diets. A total of 447 individuals with an average age ranging from 42 to 49 years participated in the studies—222 on low-carbohydrate diets and 225 on low-fat diets.

After six months, those on low-carbohydrate diets were more likely to remain on the diet and had lost more weight than those on low-fat diets. However, after 12 months, blood pressure, completion rates and weight loss were the same for both groups. After six and 12 months, individuals on low-carbohydrate diets had increased total cholesterol levels and LDL levels. However, they also had lower triglyceride levels and higher HDL or “good” cholesterol levels.

Because no trials have yet examined the risk of heart attack or death in people on low-carbohydrate diets, it’s unclear whether the beneficial effects low-carbohydrate diets appear to have on HDL and triglyceride levels cancel out their apparent negative effects on overall and LDL cholesterol levels, the authors write.

This study was supported in park by Swissmilk, Berne, Switzerland. Drs. Nordmann, Briel and Bucher are funded by grants from Santésuisse, Solothurn, Switzerland, and the Gottfried and Julia Bangerter-Rhyner Foundation, Zurich, Switzerland. Dr. Yancy is supported by a Health Services Research Career Development Award from the Department of Veterans Affairs, Washington, D.C. Dr. Yancy’s salary is funded in part by the Robert C. Atkins Foundation, Jenkintown, Pa.

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