08/06/2002 - Updated 10:34 PM ET

Researchers chew the fat on merits of the Atkins diet

By Nanci Hellmich, USA TODAY

The Atkins low-carb, high-fat diet is supposed to be simple, but it's raising complex medical and nutrition questions. Now two new studies show that those who follow the diet can lose significant amounts of weight, but other research is raising concerns about the safety of the program, linking it to an increased risk of kidney stones and bone loss.

Fueled by recent media attention and reports of successful weight loss, Dr. Atkins' New Diet Revolution by cardiologist Robert Atkins, is No. 1 on USA TODAY's Best-Selling Books List. First published in 1972, the diet allows dieters to consume steak, hamburger, pork, butter, cheese and other high-fat foods and has them cut way back on carbohydrates including pasta, sweets, some starchy vegetables and many fruits.

Some of the nation's leading obesity researchers and nutritionists are outraged by the diet, arguing that it runs contrary to the advice of most major health organizations, which advocate a diet relatively low in saturated (animal) fat and high in complex carbohydrates (grains, vegetables). Those recommendations are based on scientific evidence that a diet rich in fruits and veggies and low in saturated fat reduces the risk of heart disease, some types of cancer and other health problems.

Still, many dieters swear by the Atkins diet. And until recently, there haven't been many studies investigating its safety and effectiveness.

In one new study, conducted at Duke University Medical Center and funded by a grant from the Robert C. Atkins Foundation, participants ate a very low carbohydrate diet of 25 grams a day for six months. They could eat an unlimited amount of meat and eggs, two cups of salad and one cup of low-carbohydrate vegetables such as broccoli and cauliflower a day. Of the 50 patients enrolled, 80% adhered to the diet for the entire study, losing an average of 10% of their original body weight. The average weight lost was approximately 20 pounds, says Eric Westman, associate professor of medicine at Duke University Medical Center.

The Atkins dieters also had improvements in blood cholesterol and triglycerides, but researchers don't know if those changes are due to losing weight, cutting back on junk food or the makeup of the diet.

In another pilot study, obesity researchers at three universities recruited 63 people who were 30 or more pounds overweight and assigned them to one of two programs. One group was given a copy of Dr. Atkins' New Diet Revolution. The other group was put on a conventional diet with about 30% of calories from fat, 55% from carbohydrates and 15% from protein.

At the end of six months, those following the Atkins diet lost about 10% of their starting weight and those on the conventional diet lost about 5%. Atkins dieters also were more likely to stick with the plan than conventional dieters.

The Atkins program "may give people a way to eat fewer calories," says lead researcher Gary Foster, clinical director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine. He says researchers don't know if the benefits of losing weight outweigh the drawbacks of eating a diet high in saturated fat.

There is nothing miraculous about the Atkins diet, but if you put people on a low-calorie diet, they lose weight, says Keith Ayoob, a spokesman for the American Dietetic Association. "It's the number of calories, not where they come from."

Foster and fellow researchers are going to continue to investigate the Atkins diet with a longer-term study sponsored by the National Institutes of Health. They will look at several different aspects, including whether the diet may be more useful for some people than others and how much people are able to exercise while eating a low-carb diet. They also want to investigate why some dieters seem more likely to stick with the Atkins program than a more conventional diet.

One theory suggests that people on the Atkins diet may eat less because of a loss of appetite due to ketosis, a state in which the body partially breaks down body fat, producing organic compounds called ketones as fuel. This is due to the limited carbohydrates.

Colette Heimowitz, an Atkins spokeswoman, says the latest version of the diet book puts less emphasis on ketosis because people may not have to be in this state to lose weight on the program. She says people don't get as hungry because the fat in the plan has a positive impact on blood sugar and insulin, and protein makes people feel full longer. But other experts say these theories are unproven and need further investigation because hunger is complex.

Westman of Duke says people may get positive reinforcement from losing weight fast on Atkins, which keeps them going. Or this diet really may appeal to people who prefer to eat this way. "There are some meat lovers, and on this kind of diet you can eat a lot of meat," he says. "Still, we need more research to determine the safety of the diet."

Some researchers have concerns about several medical issues. According to a study by researchers at the University of Texas Southwestern Medical Center in Dallas, the Atkins diet may increase the risk of kidney stones and bone loss. For this study, 10 healthy subjects ate a regular diet for two weeks, then for two weeks they followed a highly restrictive, Atkins-based diet that included some vegetables but no fruits and 20 grams or less of carbohydrates a day. The participants then ate a less restrictive form of the diet for the final four weeks.

Based on blood and urine tests, researcher Chia-Ying Wang concludes that "there was an increased risk of developing kidney stones and a possible increase in the risk of bone loss." The findings are reported in the August American Journal of Kidney Diseases. "We think the diet's combination of low carbohydrates and high animal protein results in sufficient acid to increase the risk for certain kinds of kidney stones," she says.

Heimowitz says studies of six months show there is an adaptation to the program without any kidney stone formation or bone loss. But she agrees with the researchers that those following the diet should take a multivitamin and drink adequate water.

The food composition of the Atkins plan continues to trouble many experts. "You don't eat just to get thin," says Barbara Rolls, a nutrition professor at Pennsylvania State University. "You eat a good balanced variety of foods and nutrients for a lot of other reasons, which have to do with cardiovascular health, cancer protection, bone health."

Rolls and Ayoob wonder whether most people who lose weight on the diet will keep the weight off long-term by eating this way. "Do people really want to give up bananas and their favorite fruits?" Ayoob asks.

Says Rolls, "You can achieve weight loss in lots of different ways. The real challenge is to figure out a way to keep it off."

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