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Four Popular Diets All Good for Weight Loss But Not Equal for Reducing Heart Disease Risk: Presented at AHA

By Peggy Peck

ORLANDO, FL -- November 10, 2003 -- Results of a randomized comparison study suggest that any one of four popular diets -- Atkins, Ornish, Weight Watchers, or Zone -- is an effective option for weight loss and reduction of cardiac risk factors, but only the Atkins, Weight Watchers, and Zone diets achieved statistically significant reductions in Framingham scores.

Michael L. Dansinger, MD, assistant professor of medicine, Tufts University, New England Medical Center, Boston, United States, said that generally "losing 20 pounds corresponded to about a 30% reduction in heart risk score," although he explained that at this point "it isn't clear if a 30% reduction in risk score is the same as a 30% reduction in heart attacks." Dansinger presented his results at a press conference held here November 9^th at the American Heart Association's Scientific Sessions 2003.

Researchers enrolled 160 overweight men and women into the study. Most participants were 30-80 pounds overweight, and half of the volunteers were women. Patients were evenly assigned to the Atkins diet (low carbohydrates), Zone (moderate carbohydrates), Ornish (low-fat vegetarian), or Weight Watchers (moderate fat) and told to follow the diet "to the best of their ability for two months," he said. Patients were given official diet cookbooks and assigned to small group classes for diet education. For the remaining 10 months, the volunteers were told to follow their assigned diet "to whatever extent they wanted." The investigators "evaluated only the food program, not any additional lifestyle modifications such as meditation or exercise," said Dr. Dansinger.

Following the diets was not easy, he said, noting that the drop-out rate for each diet was 22% at 2 months; by 12 months, half of the volunteers assigned to the Atkins or Ornish diets had dropped out, as had 35% of those assigned to the Weight Watchers or Zone diets.

For those who stuck with the diet for 12 months, reductions in weight and Framingham risk score were 3.9% and 12.3% for Atkins (n = 21, 52% completion); 6.2% and 6.6% for Ornish (n = 20, 50% completion); 4.5% and 14.7% for Weight Watchers (n = 26, 65% completion); and 4.6% and 10.5% for Zone (n = 26, 65% completion). All diets resulted in significant (P < .05) weight loss from baseline, and all but the Ornish diet resulted in significant reductions in the Framingham risk score (P = .013), said Dr. Dansinger.

According to Dr. Dansinger, this does not mean that the "Ornish diet doesn't reduce heart disease risk. I have great faith in the Ornish diet, but it did not meet the statistical test in this study."

Dean Ornish, MD, founder and president of Preventive Medicine Research Institute, Sausalito, California, United States, was critical of the results. He said the people assigned to his diet "lost more weight, had greater reductions in LDL, and were the only dieters to significantly lower insulin -- even though the Atkins and Zone diets claim to be specifically designed to lower insulin."

Dr. Dansinger, who joined Dr. Ornish in fielding questions from reporters, agreed that the Ornish diet posted impressive results for those who stayed the course for a year: a 19.9% reduction in insulin levels, while the Atkins diet dropped insulin by 7.7%, Weight Watchers by 8.8% and the Zone by 16.5%. Likewise, the Ornish diet reduced LDL cholesterol by 16.7%, while the Atkins diet reduced LDL by 8.6%, followed by the Weight Watchers diet at 7.7%, and the Zone diet at 6.7%.

But the heart disease risk score is based on the HDL/LDL ratio, and the "Ornish diet does not increase HDL, while the other diets do achieve significant increases in HDL," said Dansinger. The Atkins and Zone diets increased HDL by 15.4% and 14.6%, respectively, while Weight Watchers posted an 18.5% gain; contrarily, the Ornish diet increased HDL by just 2.2%.

Dr. Ornish explained that HDL is not really a factor because "HDL is really like a garbage truck that goes around picking up the garbage, which is bad cholesterol. When you don't have as much bad cholesterol -- garbage -- you don't need as many garbage trucks." He added, "raising HDL is easy: Eat a stick of butter. That will drive up your HDL, but it's not good for you."

Dr. Dansinger said that HDL is a little more complicated. For example, "exercise increases HDL, and we do think that low HDL is a risk factor," he said.

"The good news about this study is that we have demonstrated that all these diets work. That means that physicians can work with patients to select the diet that is best suited to the patient. For example, if you have a patient who likes meat, it is unlikely that he or she will comply with the Ornish diet," said Dr. Dansinger.

The study was funded by a National Institutes of Health grant, the Tufts-New England Medical Center, and the USDA Nutrition Research Center at Tufts.


[Study title: One Year Effectiveness of the Atkins, Ornish, Weight Watchers, and Zone Diets in Decreasing Body Weight and Heart Disease Risk. Abstract 3535]

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