Still No Perfect Diet
A new study pits protein against carbs against fat
Pssst! Want to know the secret to losing weight? Eat less, and exercise more. Not sold? Join the club. Bookstores are brimming with shelf upon shelf of diet books, all offering their own strategies for making that spartan prescription a bit easier to stomach. The king of the bestseller list, Dr. Atkins' New Diet Revolution, the brainchild of now deceased cardiologist Robert Atkins, was first published in 1972 and sparked a low-carb, high-protein nationwide craze. The idea behind the diet is that restricting carbs-the body's preferred source of energy-prompts it to burn fat instead. Despite criticism by the medical community that the diet is unhealthful, at one point a few years ago, Americans, at the rate of 1 in 6, were turning up their noses at hamburger buns and heading straight for the burger.
Previous research has also suggested that the Atkins plan makes it easier to lose weight, and a new study lends credence to that notion. Writing in the Journal of the American Medical Association, researchers at Stanford University compared four popular, brand-name diets, with Atkins coming out slightly ahead. The study participants who gobbled up the steak, eggs, and cheese also fared better on cholesterol and blood pressure measures than those on the other diets. What's more, the women assigned to the Atkins diet lost a tad more weight. Yet experts were surprised by how little, on average, that was: just over 10 pounds, from a starting weight averaging 190 pounds. And those were the biggest losers. Women on the other diets lost less than 6 pounds. Many experts don't see the study endorsing Atkins but rather underscoring how tough a chore it is to shed inches. "There's no easy solution and no magic formula as far as weight loss goes," says Alice Lichtenstein, a nutritional biochemist with the Friedman School of Nutrition Science and Policy at Tufts University.
The other three diet regimens the researchers examined include the Zone diet by Barry Sears, a biochemist and nutrition scientist, favoring a 40-30-30 percent balance of carbs, protein, and fat, and the diet developed by internist Dean Ornish, which calls for lots of good carbs and no more than 10 percent of calories from fat. Lastly, the researchers included the LEARN (Lifestyle, Exercise, Attitudes, Relationships, and Nutrition) program, which adheres to the U.S. Department of Agriculture food pyramid and promotes a diet of about 60 percent carbs and less than 10 percent saturated fats.
The study participants, 311 premenopausal women who were obese or overweight with an average age of 41, received some initial hand-holding. But after eight weekly classes, they were on their own, armed with only the diet book to guide them. Every few months, the researchers checked the women's weight, as well as common indicators of health such as cholesterol levels. At the end of a year, the average weight loss was just over 10 pounds for the Atkins group, almost 6 pounds for the LEARN set, and nearly 5 pounds for the Ornish followers-differences so small they could have occurred by chance. Zone dieters lost just 3
Christopher Gardner, a nutrition scientist at the Stanford Prevention Research Center and lead author of the study, thinks the Atkins diet may have had an edge because it's so straightforward. "Their very simple message hits it right on the head: Drastically reduce your carbs," he says. Protein may also be more filling, and the diet's emphasis on drinking lots of water may crowd out calories from an extra gulp of an energy drink here or a half a soda there.
Regain. Of course, what works in the short term may not be a solution for the long haul. While the Atkins group lost more weight in the first six months, those participants gained some of the pounds back in the next six months. Ditto with the other diets. And Gardner emphasizes that the Atkins diet may not be a healthful choice over many years if devotees go heavy on the saturated fat. Sure, women on it got good marks on HDL cholesterol and triglycerides tests, but whether that was because of the proportion of carbs and protein or the weight loss is impossible to tell. Over time, says Gardner, high amounts of protein may knock the body out of balance, stressing the kidneys and potentially weakening bones. Jacqueline Eberstein, a nurse who worked with Atkins for 30 years and is now a nutrition consultant, says those fears are speculative and based on studies that don't apply specifically to Atkins.
These were real women in the real world, not rats in a lab, so it's no wonder that researchers also found that the participants didn't follow the diets to the letter. By the end of the study, the Atkins group was getting almost 35 percent of calories from carbs, instead of 10 percent, while the Ornish gaggle far exceeded the diet's recommendation of no more than 10 percent of calories from fat. Still, while the average weight loss was low, at least some women in every group lost significant weight.
That lack of adherence led Sears and Ornish to complain that the study wasn't a fair test. "What happens when you follow the diet is the question," says Ornish, who notes that his low-fat routine reduces heart disease. "This is the only time that Dean and I have been together on something," says Sears.
But that disconnect is exactly the point, says Marion Nestle, a nutrition professor at New York University. Anyone can dream up a diet that will shave off pounds. It's much harder to follow that diet over many years and maintain a lower weight. "What's sustainable is eating less and more healthfully and being more active," she says. That advice is the closest to a magic pill for weight loss. Unfortunately, it's one that Americans so far have been unwilling to swallow.
This story appears in the March 19, 2007 print edition of U.S. News & World Report.