Both methods can be more effective for weight loss than reducing fat intake, according to findings from Harvard.
Is there one diet that's best for losing weight? That's the debate that simmers in weight-loss circles and occasionally boils into a full diet fad. Just recall how the low-carbohydrate craze swept the nation a few years ago.
More recently, the Mediterranean style of eating -- fruit, vegetables, whole grains, fish, yogurt, as well as olive oil and wine -- caught dieters' fancy.
Now, a growing body of research suggests that the low-carbohydrate approach and the Mediterranean diet are safe and effective options to traditional dieting.
The latest findings come from a two-year Harvard study of 322 moderately obese, middle-aged Israelis. The results, published in the New England Journal of Medicine, found that "Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets." (The research was partly funded by the foundation of the late diet doctor Robert Atkins, a staunch proponent of the low-carbohydrate, high-protein approach.)
But before you add meat and butter (low-carb) to every meal or begin liberally pouring olive oil and wine (Mediterranean), know this:
"From a weight-loss perspective, it all comes down to calories," says Gary Foster, director of Temple University's Center for Obesity Research and Education.
There are a few other caveats, as well, including the fact that 86 percent of participants in the Harvard study were men. Lean, fat or somewhere in between, men have more muscle and less fat than women -- a fact that makes weight loss a little easier.
The study randomly assigned participants -- all employees of a research center in Dimona, Israel -- to either a low-fat diet, a low-carbohydrate diet or a Mediterranean diet.
Daily calorie and fat intake goals were set for those in the low-fat and Mediterranean diet groups. Women were advised to eat 1,500 calories per day; men 1,800. The low-fat group was counseled to keep fat intake at 30 percent of daily calories; the Mediterranean group at 35 percent. The low-carb group counted carbohydrates as grams rather than calories and, for the first two months, was advised to start with just 20 grams per day -- about the amount found in 1.5 slices of whole-wheat bread. Intake gradually increased to 120 grams per day.
As previous studies have shown, the low-carb group shed pounds the quickest during the first six months of the study. But after about 11 months, the Mediterranean and the low-carbohydrate groups were not statistically different. Both shed more weight than the low-fat group. On average, the low-fat group lost about 6 pounds, the Mediterranean group about 8 pounds and the low-carb group 10 pounds.
Women did best on the Mediterranean diet, losing about 13 pounds compared with 5 pounds for the low-carbohydrate diet and just 2 pounds for the low-fat approach.
"That was a surprise," said Meir Stampfer, professor at Boston's Brigham and Women's Hospital and a co-author of the study.
But with only 45 women in the study, he says not to "put too much weight" on the finding until it's studied more.
Men and women on all three diets significantly whittled their waistlines and improved blood pressure, but no diet proved best. Levels of the hunger hormone leptin also improved on all three diets. So did the "good" cholesterol -- high-density lipoprotein -- as well as triglycerides -- unhealthy fats that contribute to heart disease. The low-carbohydrate diet produced the biggest gains for both.
On the other hand, low-density lipoprotein , a type of "bad" cholesterol, did not change significantly on any of the diets.
"The first take-home message is that if you are embarking on weight loss, start with a low-carbohydrate or Mediterranean diet," Stampfer said.
That doesn't mean "eating cheeseburgers and throwing away the bun," he said.
Participants were urged to eat fish and chicken without the skin, as well as dairy products. The choice of healthy protein is "one of the key points," Stampfer said.
On all three diets, weight loss took focus and commitment.
"You can lose weight," Stampfer said. "But it is hard, and it is not going to happen rapidly."
Sally Squires writes for the Washington Post.