ATLANTA?The Atkins diet may have proven itself after all: A low-carb diet and a Mediterranean-style regimen helped people lose more weight than a traditional low-fat diet in one of the longest and largest studies to compare the dueling weight-loss techniques.

A bigger surprise: The low-carb diet improved cholesterol more than the other two approaches. Some critics had predicted the opposite.

The study is remarkable not only because it lasted two years, much longer than most, but also because of the huge proportion of people who stuck with the diets?85 percent. More than 82 percent of the dieters were men, with an average starting weight of just over 90 kilograms (200 pounds).

After two years, the dieters lost an average of 2.95 kg (6.5 lb) on the low-fat regimen, 4.54 kg (10 lb) on the Mediterranean diet and 4.67 kg (10.3 lb) on a mostly vegetarian version of the low-carbohydrate Atkins diet, Israeli researchers reported on Wednesday.

All three approaches achieved not only weight loss but also improved cholesterol profile.

Improving cholesterol

The low-carb diet, however, excelled in improving the cholesterol profile, reducing the ratio of total cholesterol to good cholesterol by 20 percent, compared to just 12 percent in the low-fat diet.

?The good news is, we have alternatives,? said Iris Shai of Ben-Gurion University of the Negev, who led the study that was published in the New England Journal of Medicine.

?If we fail in one strategy, we may want to choose another diet. We cannot think any more that one diet fits all,? Shai added in a telephone interview. ?This study will open clinical medicine to considering low-carb and Mediterranean diets as safe alternatives for patients.?

Controlled environment

The research was done in a controlled environment?an isolated nuclear research facility in Israel, where the volunteers worked. The 322 moderately obese participants got their main meal of the day?lunch?at the central cafeteria.

The cafeteria prepared healthy dishes for each group of dieters every day. The appropriate foods for each diet were identified with colored dots, using red for low-fat, green for Mediterranean and blue for low-carb.

?The workers can?t easily just go out to lunch at a nearby Subway or McDonald?s,? said Dr. Meir Stampfer, the study?s senior author and professor of epidemiology and nutrition at the Harvard School of Public Health.

As for breakfast and dinner, the dieters were counseled on how to stick to their eating plans and were asked to fill out questionnaires on what they ate. The researchers coached spouses on how to help the participants at home.

Diet restrictions

Both the low-fat and Mediterranean diets restricted calories. The Mediterranean diet had the most dietary fiber and monounsaturated/saturated fat?so-called healthful fats. The low-carb diet had the most fat, protein and dietary cholesterol.

?The low-fat, restricted-calorie diet was based on American Heart Association guidelines. We aimed at an energy intake of 1,500 calories per day for women and 1,800 calories per day for men, with 30 percent of calories from fat, 10 percent of calories from saturated fat, and an intake of 300 mg of cholesterol per day,? the researchers wrote.

?The participants were counseled to consume low-fat grains, vegetables, fruits and legumes and to limit their consumption of additional fats, sweets and high-fat snacks.?

Vegetables, red meat

The Mediterranean diet also limited calories to 1,500 for women and 1,800 for men. The diet was rich in vegetables and low in red meat, with poultry and fish replacing beef and lamb, and fat coming from olive oil and a few nuts each day.

The Atkins low-carb diet reduced intake for processed carbohydrates, but set no limits for calories or fat. ?However, the participants were counseled to choose vegetarian sources of fat and protein and to avoid trans fat,? the researchers said.

?So not a lot of butter and eggs and cream,? said Madelyn Fernstrom, a University of Pittsburgh Medical Center weight management expert who reviewed the study but was not involved in it.

While most of the participants were men, all men and women in the study got roughly equal amounts of exercise.

Weight loss, cholesterol

After two years, dieters on the low-carb diet had the biggest weight loss, closely followed by those on the Mediterranean diet. Those on the low-fat regimen registered the smallest weight loss.

More surprising, however, were the measures of cholesterol. While acknowledging that an Atkins-style diet could help people lose weight, critics have said that over the long term, the same weight-loss technique may drive up cholesterol because it allows more fat.

The low-carb approach, however, seemed to have triggered the most improvement in several cholesterol measures, including the ratio of total cholesterol to HDL?the ?good? cholesterol. For example, someone with total cholesterol of 200 and an HDL of 50 would have a ratio of 4 to 1. The optimum ratio is 3.5 to 1, according to the American Heart Association.

Doctors consider the ratio an indicator of a patient?s risk for hardening of the arteries. ?You want that low,? Stampfer said.

The ratio declined the most (20 percent) in the low-carb dieters. The Mediterranean dieters saw a 16-percent drop in their cholesterol ratio compared to 12 percent for low-fat dieters.

?A vindication?

?It is a vindication,? said Abby Bloch of the Dr. Robert C. and Veronica Atkins Foundation, a philanthropy group that honors the Atkins? diet?s creator. The foundation was the study?s main funder, but it played no role in the study?s design or reporting of the results.

The study is not the first to offer a favorable comparison of an Atkins-like diet. Research published in the Journal of the American Medical Association last year found overweight women on the Atkins plan had slightly better blood pressure and cholesterol readings than those on the low-carb Zone diet, the low-fat Ornish diet and a low-fat diet that followed US government guidelines.

The heart association has long recommended low-fat diets to reduce heart risks, but some of its leaders have noted the Mediterranean diet has also been proven safe and effective.

More restrictive

The heart association recommends a low-fat diet even more restrictive than the one in the study, according to Dr. Robert Eckel, the association?s past president who is a University of Colorado-Denver professor of medicine.

The association does not recommend the Atkins diet. According to Eckel, however, a low-carb approach is consistent with the heart association?s guidelines so long as there are limitations on the kinds of saturated fats often consumed by people on the Atkins diet.

The new study?s results favored the Atkins-like approach less when subgroups such as diabetics and women were examined.

Among the 36 diabetics, only those on the Mediterranean diet lowered blood sugar levels. Among the 45 women, those on the Mediterranean diet lost the most weight.

?I think these data suggest that men may be much more responsive to a diet in which there are clear limits on what foods can be consumed,? such as an Atkins-like diet, said Dr. William Dietz, of the Centers for Disease Control and Prevention.

?It suggests that because women have had more experience dieting or losing weight, they?re more capable of implementing a more complicated diet,? said Dietz, who heads the center?s nutrition unit.