On average, women taking the Atkins diet lost 10.4 pounds after 12 months. The average weight loss was 5.7 pounds for women on the LEARN diet, 4.8 pounds for those on Ornish diet and 3.5 pounds for those following the Zone weight-loss plan.

"Many health professionals, including us, have either dismissed the value of very low-carbohydrate diets for weight loss or been very skeptical of them," said lead researcher Christopher Gardner of the Stanford Prevention Research Center in California.

"But it seems to be a viable alternative for dieters."

The US$2-million study included 311 premenopausal, non-diabetic, overweight women who were randomly assigned to follow either the Atkins, Zone, LEARN (Lifestyle, Exercise, Attitudes, Relationships and Nutrition) or Ornish diets. The participants received eight hours of instruction from a dietitian.

The Atkins diet has the lowest percent of carbohydrates. The Zone diet has a 40:30:30 ratio of carbohydrate, protein and fat. The LEARN diet is low in fat and high in carbohydrates. The Ornish diet is high in carbohydrate and extremely low in fat.

After the stipulated time BMI, trigyceride levels and blood pressure of all participants were evaluated and the results showed that body mass index, triglycerides and blood pressure of women following the Atkins diet had decreased in comparison to women in the other three groups.

Their high-density lipoprotein (HDL), had increased compared to that of women on the other three diets.

"The research had a good concept and incredibly pathetic execution," Zone diet creator Barry Sears told The Associated Press.

"It's a lot easier to follow a diet that tells you to eat bacon and brie than to eat predominantly fruits and vegetables," said Ornish.

Gardner believes the success of the Atkins diet is its "very simple message: Get rid of all refined carbohydrates to lose weight."

Dr. Arya Sharma, chair of cardiovascular obesity research at McMaster University, said "Patients are less hungry and tend to eat less overall with these diets than with other diets where there are more or less restrictions in the kinds of foods that patients can eat." "So it's not surprising that patients lost more weight on the Atkins diet."

"If after eight hours of education with a dietitian and a financial incentive ($150) to complete this program well, the best or the average weight loss a person can get off Atkins is 10 pounds, that's not so exciting," Freedhoff said from Ottawa. "What matters are the calories in your food."

Critics argue that the study doesn't answer the chief concern about the Atkins diet, 'whether consistently eating all that fatty food leads to long-term health problems.'

Sharma added, "What's quite clear is that patients who have obesity and need to lose weight and keep that weight off cannot eat like other people. Diet is only one part of the obesity treatment plan. Physical activity is as important, particularly when it comes to maintaining the weight loss."