A Judgment on Heart Benefits of Best-Selling Diets

WORCESTER, Mass., Oct. 1 -- In a collision of the best-selling weight-loss books, the neovegetarian fare pushed by the Ornish diet earned heart-healthy honors, according to the standards of an index that dices the risks of fats and carbohydrates.

The investigators used the Alternate Healthy Eating Index, a Harvard School of Public Health system that refines that the USDA rating system to isolate dietary components that are most strongly linked to cardiovascular disease risk reduction.

The authors found better -risk scores with the Ornish system than with diverse competitors such as New Glucose Revolution, Weight Watchers, Atkins, South Beach, and Zone plans.

The Weight Watchers high-carbohydrate plan was runner-up, followed by the New Glucose Revolution diet, wrote Yungsheng Ma, M.D., Ph.D., of the University of Massachusetts in the October issue of the Journal of the American Dietetic Association

The diet plans' bottom feeders were those calling for a sparing use of carbohydrates and lavish amounts of protein. Thy included the Atkins/100-g carbohydrate diet, South Beach/Phase 3 plan, and Atkins/45-g carbohydrate diet, the investigators reported.

"The Ornish plan, which is almost a completely vegetarian plan, scored high largely due to the amount of vegetables, fruit, cereal fiber intake, and low trans fat," the investigators wrote. "The Weight Watchers higher-carbohydrate and the New Glucose Revolution plans also fared well due to the emphasis on fruits and vegetables, higher whole-grain composition, and low trans fats."

The lowest-scoring Atkins/45-g carbohydrate plan, with the least amount of fruit and cereal fiber and the highest amount of red meat and trans fats, has been shown to improve cardiovascular disease risk factors, including triglycerides in the short term, the authors acknowledged.

They noted, however, that "recent metabolic studies showed detrimental effects of trans fat on inflammatory factors and indicators of insulin resistance," and that "epidemiologic studies have indicated that the magnitude of association between trans fat and cardiovascular disease is stronger than for saturated fat."

The investigators consulted the New York Times' list of bestsellers for five years for candidate plans. They also included Weight Watchers plans because they are the largest commercial weight-loss plans, and the USDA's 2005 Food Guide Pyramid plan, which carries the federal government's stamp of approval.

The investigators chose to compare the dietary values of the various plans against the Alternate Healthy Eating Index, which was developed at the Harvard School of Public Health in response to concerns that the USDA's Healthy Eating Index does not distinguish between different types of fats and carbohydrates.

Applied to data on more than 100,000 participants in the Nurses' Health Study and the Health Professionals' Follow-up Study, the Alternate Healthy Eating Index was twice as good as the USDA's index at predicting cardiovascular disease risk from diet (McCullough ML and Willett WC, Public Health Nutr. 2006;9:152-157).

The authors used published sample menus from the various diet plans to determine nutrition value and to calculate dietary quality according to the index criteria. The rating scale gives a top score of 70 to those diets with what the Harvard researchers consider the right balance of fruits, vegetables, nuts and soy, ratio of white to red meat, cereal fiber, trans fats, ratio of polyunsaturated fat to saturated fat, alcohol, and duration of multivitamin use.

Dr. Ma and colleagues excluded from their analysis the alcohol and multivitamin components of the Alternate Healthy Eating Index because those elements were not included in the sample menus used to judge the plans.

They used of analysis of variance to compare nutrient information among the weight-loss plans, and compared index scores adjusted for energy content.

They found that of a maximum possible 70, the scores for each weight-loss plan from the highest to the lowest were:

• Ornish: 64.6
• Weight Watchers high-carbohydrate: 57.4
• New Glucose Revolution (a low glycemic index weight-loss plan): 57.2
• South Beach/Phase 2 (lean protein and low-fat dairy, with gradual reintroduction of whole-grain carbohydrates and fruit): 50.7
• Zone (reduced carbohydrate, low-energy diet): 49.8
• 2005 Food Guide Pyramid: 48.7
• Weight Watchers high-protein: 47.3
• Atkins/100-g carbohydrate: 46
• South Beach/Phase 3 (expanded quantity and selection of whole grains and particular fruits and vegetables): 45.6
• Atkins/45-g carbohydrate: 42.3.

"An unexpected finding was that after adjusting for energy content, the 2005 Food Guide Pyramid plan, which is based on the Dietary Guidelines for Americans 2005, fared significantly worse than the New Glucose Revolution, Weight Watchers higher carbohydrate, and Ornish plans," the investigators wrote. "The 2005 Food Guide Pyramid plan was devised to prevent nutrient deficiencies. Nutrient deficiencies relate to physiological requirements, but are not an objective measure that correlates with the prevention of cardiovascular disease."

The authors acknowledged several study limitations, including the assumption of perfect adherence to the diets, inclusion of only eight diet plans and their components, exclusion of dietary supplement, a lack of validation about the effect of the Alternate Healthy Eating Index on chronic disease, and the reliance on only seven days of menus for each plan, which could have caused the study to be underpowered.