Battle of the Diet Plans

Americans spend $60 billion a year on diets, pills, and programs in the hope that the weight loss approach they choose will ultimately triumph over others. Although there are many diets in contention, a clear winner has yet to emerge. As obesity rates continue to rise dramatically worldwide, scientists have recognized the need to test the effectiveness of the most widely used plans. Over the past two years, three notable university-based studies (one from Stanford, a second from Harvard and the Ben-Gurion University of the Negev, and a third from the University of Missouri) have pitted some of the leading diets against one another—and, in the last case, against exercise—to determine which approach offers the best results. Their conclusions may surprise you, so before you spend any more money or time fretting over the most recent diet aid, check out the results of the matchups.

The contenders:

Low carb (including Atkins)

Advises lots of protein, mostly in the form of meat at every meal, and restricts carbohydrates. Thirty percent of your calories will come from protein, 50 percent from fat, and about 20 percent from carbs, especially veggies and fruit.

Low fat (such as Weight Watchers)

Emphasizes grains, fruits, and vegetables and allows modest servings of meat. Portion control is key. About 50 percent of your calories will come from carbohydrates, 30 percent from fat, and 20 percent from protein.

Zone

Balances carbohydrates, fat, and protein, theoretically to stabilize hormones that trigger hunger and weight gain. Thirty percent of the calories you eat will be fat, 40 percent carbohydrates, and 30 percent protein.

Mediterranean

Prescribes grains, vegetables, and sources of healthy fats such as olive oil and nuts. About 45 percent of your calories on this plan will come from carbohydrates, 35 percent from fat, and 20 percent from protein.

Ornish

Is an extremely low-fat vegetarian diet that recommends forgoing nuts, meat, and fish. Roughly 70 percent of your calories will come from carbohydrates, 20 percent from protein, and 10 percent from fat.

Match 1: Low carb vs. low fat vs. Mediterranean

Number of dieters: Low carb, 109; low fat, 104; Mediterranean, 109.

Average pounds lost at six months: Low carb, 14; low fat, 10; Mediterranean, 10.

Final loss (two years): Low carb, 12 pounds; low fat, 7; Mediterranean, 10.

The details: Most of the dieters in this 2008 study published in The New England Journal of Medicine (and paid for in part by the Atkins Research Foundation) were men. The women actually lost more pounds on the Mediterranean approach, but the finding wasn't conclusive. As is true in most diet studies, weight loss peaked at around six months, after which dieters began to put pounds back on. All groups saw improvements in cholesterol, insulin, glucose, triglyceride, and blood pressure levels.

Match 2: Low carb vs. low fat vs. Zone vs. Ornish

Number of dieters: Low carb, 77; low fat, 79; Zone, 79; Ornish, 76.

Average pounds lost at six months: Low carb, 14; low fat, 9; Zone, 6; Ornish, 6.

Final loss (one year): Low carb, 10 pounds; low fat, 6; Zone, 4; Ornish, 5.

The details: Low carb (Atkins) was the victor in this 2007 study published in the Journal of the American Medical Association. These dieters also saw their heart disease risk factors—blood pressure, cholesterol, triglyceride levels—plummet at least as much as they did for people on the heart-healthy low-fat and Ornish diets. Again, most of the pounds were shed in the first six months, with many people gaining back some weight. By the end, in fact, many had stopped following their prescribed diets closely.

Match 3: Low fat vs. exercise

Number of dieters: Low fat, 24; exercise, 19.

Average pounds lost at six weeks: Low fat, 6; exercise, 2.

Final loss (three months): Low fat, 9 pounds; exercise, 3.

The details: In a 2008 study published in the Journal of Exercise Physiology, a group of dieters followed a low-fat plan, while exercisers stuck to their usual eating patterns and worked out at least three days a week for 50 to 60 minutes at a gym. Though the dieters shed more pounds, some of the loss was in the form of calorie-burning muscle (the exercisers kept their muscle mass). As the researchers point out, muscle is key to helping dieters maintain weight loss. The results demonstrate the need to combine exercise and dieting.

And the winners are…

Low carb and exercise

A low-carb diet consistently produced the greatest weight loss, so this plan—combined with exercise—seems to be a good place to start. "I'm a proponent of that approach if it means you'll eat fewer junky carbs," says Christopher Gardner, Ph.D., associate professor of medicine at Stanford University and lead author of the study in Match 2 (above). But Gardner says dieters may need to try more than one plan before they find success. "We are all so different—a diet that works for me may not work for you," he says. Although low carb won in terms of average weight loss, each diet had a few adherents who managed to lose 30 to 40 pounds. "What's more important than diet type is how closely you can adhere to it," says Gardner.

The truth is, says Meir Stampfer, M.D., of the Harvard School of Public Health and an author of the Match 1 study, "there is more than one way to go for weight loss, so don't get discouraged."