Dietary quality of popular diets varies: study

By Amy Norton

NEW YORK (Reuters Health) - There's no shortage of weight-loss plans for Americans to choose from, but some of the most popular ones fall short in dietary quality, according to a new study.

In an analysis of eight popular diets, researchers found that the Ornish plan, the Weight Watchers High-Carbohydrate diet, and the New Glucose Revolution plan came out on top in terms of nutritional quality and potential effects on heart health.

What the plans all had in common were high amounts of fruits, vegetables and fiber, and low amounts of artery-clogging types of fat, researchers found.

At the bottom of the list came the high-protein, low-carbohydrate Atkins plan, mainly because of its more liberal attitude toward red meat, saturated fat and trans fats, and low amounts of fruit and fiber.

The findings are published in the Journal of the American Dietetic Association.

For overweight and obese adults, it's important not only to shed pounds, but to do it by eating heart-healthy foods, explained Dr. Yunsheng Ma, the study's lead author and an assistant professor of medicine at the University of Massachusetts Medical School in Worcester.

"Obese people already have a higher risk of heart disease," Ma told Reuters Health. So it's particularly important that they make heart-healthy diet changes that can be kept up for the long haul, the researcher noted.

For their study, Ma and colleagues used a measure called the Alternate Healthy Eating Index (AHEI) to judge the quality of eight widely used diet plans. They picked six of the diets from the New York Times bestseller list; they also included the Weight Watchers plan, as it is the largest commercial plan in the U.S., as well as the federal government's 2005 Food Guide Pyramid, since it offers diet guidelines to all Americans.

The AHEI evaluates a diet's potential heart benefits based on factors such as the amount of fruits, vegetables and fiber, and the ratio of heart-healthy polyunsaturated fats to cholesterol-raising saturated fat.

The top score went to the Ornish diet, a low-fat, largely vegetarian plan that allows some non-fat dairy and egg whites. The diet, developed by Dr. Dean Ornish, is intended to prevent and treat heart disease, so its high score -- 64.6 out of a possible 70 points -- is not unexpected.

Also scoring well, at just over 57 points, were the Weight Watchers High-Carbohydrate and the New Glucose Revolution diets -- which, like Ornish, contain high amounts of fruits, vegetables and fiber-rich grains.

The Glucose diet is based on the concept of the glycemic index; it limits simple carbohydrates that cause quick blood-sugar spikes -- like potatoes and white bread -- but allows complex carbohydrates higher in fiber and other nutrients.

The Atkins plan and some other low-carb, high-protein diets, including the Weight Watchers High-Protein option, were deemed less heart-healthy.

Surprisingly, Ma said, the government's Food Pyramid landed in the middle. Though the Pyramid was revamped in 2005, it still fall shorts of the top-ranked diets as far as fruits, vegetables, fiber and limits on "bad" fats, Ma noted.

The researchers are not advocating any one particular brand of weight-loss plan. But, according to Ma, people who are trying to lose weight can look to the components of the top-scoring diets to help fashion a heart-healthy eating plan.

SOURCE: Journal of the American Dietetic Association, October 2007.