Politi: "food industry makes it difficult for even the well-informed consumer to make healthy choices" Photo: Les Todd

"It's going to be a tremendous expense for us as a society," he adds. "It will affect us in terms of productivity. People who are sick and unhappy don't function as well. And as these children become obese, their own children are set up. The likelihood that a child will have weight problems is 80 percent if both parents are obese."

How to stop or, better yet, reverse America's obesity epidemic? For nutritionists and obesity experts, that's the $64,000 question. The late Robert Atkins, who dedicated his life to creating a dieting empire, blamed carbohydrates. Deprive the body of carbs, he preached, and your body will enter a fat-burning state called ketosis that will shed pounds.

Eric Westman, an associate professor of medicine at Duke, didn't buy Atkins' weight-loss sermon and, after reading his best-selling book, Dr. Atkins' New Diet Revolution, was convinced the Atkins plan had little scientific merit. "It's a very slick book, written to sell books," he says. Westman even advised his overweight patients against trying Atkins, warning them that the added fat that accompanied their high-protein regime would raise their cholesterol and triglyceride readings. But when three former patients disregarded his advice and returned to his office in 1997 trimmer and with improved triglyceride and cholesterol readings, Westman figured he had to learn more.

"So I wrote Atkins a letter and basically told him, 'Your ideas are intriguing, but where are your data?' " Not long after that, Westman received a surprise telephone call from the diet guru himself. After listening to Westman's complaint about the lack of medical data on low-carb diets, Atkins agreed to finance a study at Duke to determine whether the changes Westman had seen in his former patients would also show up in a randomized clinical trial.

Westman and his colleague, William Yancy, an assistant professor of medicine at Duke, published the results of their first low-carb study in the July 2002 issue of the American Journal of Medicine. They put fifty obese patients on a very low carbohydrate diet--amounting to some 25 grams per day, or about two cups of salad and one cup of a low-carbohydrate vegetable such as broccoli or cauliflower--for six months. The result: Some 80 percent of the patients lost an average of 10 percent of their body weight, or about 20 pounds.

"The most counterintuitive thing was that their cholesterol levels did not get worse, even though they could eat an unlimited amount of meat and eggs," says Westman. "Their LDL, or bad cholesterol, on average, did not get worse, and their triglycerides went down a lot. Their HDL, the good cholesterol, went up. This was interesting. So we went back to the Atkins Center and said, 'You need to fund a randomized clinical trial, because some of these people had been on the Atkins diet before and knew it would work.' "

That follow-up study, involving 120 obese patients randomly assigned for six months to either the traditional low-fat diet recommended by the American Heart Association or the Atkins plan, produced a few other surprises. The study, published in the May 18, 2004 issue of the Annals of Internal Medicine, found that low-carb dieters not only lost more weight than the low-fat dieters--an average of twenty-six pounds compared with fourteen pounds--they also lost more body fat, lowered their triglyceride levels, and raised their HDL more than the low-fat group. "The mechanism for the weight loss seems to be a reduction in calories," says Yancy. "There might be some other things that are contributing slightly, such as the thermic effect of food; that is, the body actually wastes energy when it eats, and a high- protein diet might increase that effect. But I think it's really that people are reducing their caloric intake. And the interesting thing is that people seemed to do that on their own. They said it was different from other diets because they weren't hungry all the time. We had a lot of people who said they didn't eat as many meals because they just weren't hungry for lunch or breakfast."

"The current paradigm explaining why this diet works is: It's higher protein, and protein is satisfying," adds Westman. "What most people who haven't studied this diet don't understand is that there is also an appetite suppression. It can't be the protein if you haven't eaten anything and you're not hungry. So the unknown question is, What causes the appetite suppression with people on this diet?"

Westman and Yancy's results parallel two other studies published in the past year that found low-carb diets to be at least as effective in losing weight as low-fat diets, for at least the first six months. But whether low-carb dieters regain their weight and whether these individuals suffer any medical problems when they continue their diets beyond six months remain open questions. "No one really knows," says Westman. "There are people who have done the diet for years, but not in a large enough number and not with monitoring to know that they're healthy by all of the parameters that we can measure. In both of these studies, I closed up shop after six months and told the patients, 'I'm not even sure you should be on this diet.'"

As a practical matter, both Westman and Yancy counsel their overweight patients not to go low-carb for longer than six months. And when restricting carbs, the researchers insist that dieters be monitored by a physician, particularly if they have diabetes or high blood pressure. "This really shouldn't be your first method of losing weight," advises Westman. "But over the last six months, I've come to the conclusion that if you've tried other ways of losing weight unsuccessfully and if obesity is your main problem, then this is a viable option with monitoring. The times are changing quickly, and a lot of it has to do with ongoing research."

That revisionist view on low-carb diets, combined with heightened public interest in Atkins, South Beach, and other low-carb regimes, prompted Eisenson and Politi to begin last fall what they call a "moderate low-carb diet" at the Duke Diet & Fitness Center. About 30 percent of the center's overweight patients now choose this diet, in which 35 percent of their calories come from carbs, 30 percent from protein, and 35 percent from fat.

"We've found that a lot of our clients who pick that option do extremely well," says Politi. "It's a diet that includes whole foods. They can eat fruit, which is very nutritious and shouldn't be eliminated from the diet as some low-carb diets recommend, and good grains--those high in fiber and not processed, such as oatmeal, sweet potato, corn, and peas. It's a good ratio of nutrients for people who are not very physically active. And, as they lose weight and become more active, I think it would be okay for them to eat 55 to 60 percent of their calories from carbohydrates, as the major health organizations recommend."

Politi and Eisenson, however, don't think people should adopt low-carb as a lifestyle, especially if they are active and are simply looking to lose five or ten extra pounds. "Low fat is an all-inclusion diet," Politi says. "Low carb is a diet in which a lot of important foods are not allowed. The restrictive diets are not the ones that are normally successful for the long haul. So I'm skeptical that low-carb diets are going to solve the obesity problem. That said, I strongly believe that there is no diet that fits everyone. And I think our major health organizations need to come up with different diet recommendations, depending on whether we're young and more active or older and more sedentary."

One useful outcome of the current low-carb craze is that people are now paying more attention to limiting their refined carbs, eating more vegetables and other complex carbohydrates, and avoiding overindulging in foods just because they're low in fat.