Atkins Pounds Other Popular Diets in U.S. Test

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Other bestselling diet books have offered alternative routes to leaner physiques. The hugely popular Zone diet advocates a daily rationing of food energy: 40 percent from carbohydrates, 30 percent from protein and 30 percent from fat.

Cardiologist and lifestyle guru Dr. Dean Ornish has developed his own plan. The popular Ornish diet urges users to drastically cut their fat intake to below 10 percent of daily calories.

Rounding out the four studies included in the new trial is a lesser-known regimen, the Lifestyle, Exercise, Attitudes, Relationships and Nutrition (LEARN) diet -- a more moderate diet modeled on the Food Pyramid. LEARN, which is favored by many nutritionists, allows participants to indulge in foods from all groups but emphasizes portion control, regular exercise and changes in eating behaviors.

In their study, the Stanford group randomized the 311 healthy but overweight premenopausal women to one of the four diet plans.

Because high dropout rates have plagued previous comparison trials, nutritionists were on hand to encourage ongoing participation. Women were even given a modest stipend to help keep them on their respective diets over the 12 months of the study.

"The basis of this study was our total frustration that popular diet books are out there saying the exact opposite things and all swearing they are they way to go," Gardner said. To test each regimen's effectiveness, his group had the women follow their particular diet's instructions to the letter.

In one sense, all of the diets won, since "all of the women did succeed in losing weight on average," Gardner said. "They all got a little better blood pressure and cholesterol," too.

Women on Atkins experienced much better weight loss, however. Gardner said he only has theories as to why. One reason might be the simplicity and timeliness of the plan's central message, he said.

"If you look at the last couple decades in American dietary changes, calories have been creeping up due to refined carbohydrates -- sodas, high-fructose corn syrups, snack foods," he said. "I think that Atkins may have been right on the money in terms of the thing that's been causing us to gain weight."