Low Carbs, Not Protein or Fat, Key to Weight Loss

In a small-scale study, Australian researchers found that a low-carbohydrate diet, whether combined with high fat or high protein, will enable a dieter to lose weight. Fifty-seven overweight and obese volunteers went on either a low-carb diet with high protein/low fat or a low-carb diet with high fat/moderate protein. The low-carb/low-fat/high-protein diet included larger portions of lean meat, fish, and dairy products. The low-carb/high-fat/low-protein diet included monounsaturated fats from nuts and canola oil as well as moderate portions of lean meat and dairy. In both regimens, carbohydrates made up one third of the daily calories.

Both regimens were equally successful for weight loss and aided the participants'cholesterol, blood sugar, and insulin. After 12 weeks, both men and women in the study had lost an average of 20 lb. They did not take off any more weight in the 4 weeks post diet, when they replaced carbs with protein or fat without cutting calories. Currently, there are no data on the long-term effects of either regimen, although there is concern that the higher-fat diet will have adverse effects on the heart, kidneys, and blood vessels.

One result in favor of the high-protein regimen was a decrease in the "thermic effect of feeding,"whereby they burned calories by merely metabolizing their food?an effect not seen by the high-fat group. Dr. Peter M. Clifton of the University of Adelaide commented, "Either diet would be sustainable in the long term?. It is possible that, after 1 to 2 years, the high-protein diet could end up spurring greater weight loss."

Ms. Farley is a freelance medical writer based in Wakefield, RI.