Low-carb diet speeds initial weight loss: study

NEW YORK (Reuters Health) - In a study of overweight and obese people, those who went on a low carbohydrate diet lost more weight -- and more fat -- than their peers who went on a low-fat, portion-controlled diet.

After 12 weeks on the low-carb plan, study participants had lost an average of 4.9 kilograms (10.8 pounds), compared to 2.5 kg (5.5 pounds) for their peers on the low-fat diet.

However, after the weight-maintenance phase of the study, which lasted another 24 weeks, differences between the two groups in weight loss and fat mass remained, but were no longer statistically significant.

The findings confirm that the low-carb diet tested in the study is a "reasonable alternative" to cutting fat and controlling portions in order to maintain a healthy weight, Dr. Kevin C. Maki of Radiant Research in Chicago and colleagues conclude.

The approach Maki's team tested -- a reduced-glycemic-load (RGL) diet -- required people to restrict their carbohydrate intake and eat more low glycemic index (GI) foods, meaning foods that produce a relatively small, gradual increase in blood sugar levels. Low GI foods generally are rich in fiber, consist of more complex carbohydrates, and include vegetables, beans and whole grains.

Study participants on the RGL diet did not eat certain high-carb foods, such as fruits and starches, for the first two weeks, and also abstained from alcohol, after which they introduced low-GI foods and were allowed to drink moderate amounts of alcohol. But they were allowed to eat as much of the permitted foods as they wanted. Those on the low-fat diet were instructed to reduce their energy intake 500 to 800 calories per day by eliminating high-fat foods and controlling portion sizes.

After 12 weeks, study participants in either group could continue on the weight loss diet or switch to a weight maintenance plan.

At 12 weeks, the low-carb group had lost significantly more weight, and also more fat -- 1.9 kg (4.2 pounds) of fat vs. 0.9 kg (2 pounds) for the low-fat diet group.

By 36 weeks, the low-carb group had kept off 4.5 kg (10 pounds), compared to 2.6 kg (5.7 pounds) for the low-fat group, not a huge difference.

Low-carb diet participants had maintained a 2 kg (4.4 pounds) loss of fat weight, compared to 1.3 kg (2.9 pounds) for the low fat group, which again was not a significant difference.

The researchers say more research is needed to clarify the mechanisms responsible for the greater initial losses of body weight and fat associated with the RGL diet, to evaluate the persistence of these losses over longer treatment periods, and to obtain greater insight into strategies that would improve long-term weight-loss maintenance."

SOURCE: American Journal of Clinical Nutrition, March 2007.