MONDAY, May 17, 2004 (HealthDayNews) -- Two new studies seem to provide further evidence that a low-carbohydrate regimen is at least as effective as a low-fat diet in helping people drop excess weight without harming their cholesterol levels.

The studies described in the May 18 issue of the Annals of Internal Medicine support the late Dr. Robert Atkins, the controversial New York cardiologist who popularized a high-protein, high-fat approach that severely restricts carbohydrate consumption.

In both studies, low-carb dieters lost more weight at the end of six months than people on a low-fat diet. They also had lower levels of triglycerides -- blood fats that can raise the risk of heart attack or stroke -- and improved levels of high-density lipoprotein (HDL), the so-called "good" cholesterol.

After a year, people on the low-carb diet had better triglyceride and HDL levels than those on a conventional low-fat diet, although weight loss was similar between the two groups.

"Clearly, all of these studies show that a low-carb diet is an option for people," said Dr. William S. Yancy, a research associate at the Veterans Affairs Medical Center in Durham, N.C., and lead author of one of the studies.

Critics, however, remain unconvinced. These short-term studies do not measure the potential long-term risk for heart disease, the nation's top killer. Without solid evidence, no one really knows whether the Atkins approach can produce lasting weight loss without damaging the heart, they say.

"The public has been misled enough already," said Dr. Robert H. Eckel, a nutrition spokesman for the American Heart Association, and a professor of medicine and physiology at the University of Colorado Health Sciences Center in Denver.

Skeptics also point to a potential conflict of interest. One of the studies was supported by a grant from the Robert C. Atkins Foundation.

Atkins died in April 2003 after a severe head injury left him comatose, but his unconventional weight-loss approach has persevered. The Atkins diet gained new respect last May when two studies in the New England Journal of Medicine suggested the plan is more effective than a traditional low-fat diet in helping people shed unwanted pounds without boosting their cholesterol levels.

The new studies seem to bolster those results.

One study is believed to be the longest and largest low-carb vs. low-fat face-off to date, involving people with diabetes or who are at high risk of cardiovascular disease.

Lead author Dr. Linda Stern, an internal medicine physician at the Philadelphia Veterans Affairs Medical Center, and colleagues followed 132 obese adults over a 12-month period. Eighty-three percent of them had diabetes or metabolic syndrome, a combination of disorders that can lead to greater risk of diabetes, heart disease, or stroke.

Participants were randomly assigned to either a restricted carbohydrate diet -- less than 30 grams of carbohydrates a day -- or a conventional diet that cut caloric intake by 500 calories a day, with less than 30 percent of calories from fat.

At six months, the low-carb dieters lost more weight than the low-fat group. By 12 months, though, their weight loss was similar -- roughly 11 to 19 pounds for the low-carb group and seven to 19 pounds for the low-fat group.

The difference is that the low-carb group maintained most of its six-month weight loss over the year, while the low-fat group continued to lose weight after six months. Another key difference is the low-carb group's blood fat levels decreased more, and their good cholesterol decreased less than the low-fat dieters.

The findings may be limited because of a high dropout rate, the authors concede. Overall, 34 percent ended their participation before the study was completed. Twenty were on the low-carb diet and 25 were on the conventional diet.

"I think at this point I have no compunctions recommending to patients cutting out simple carbohydrates," Stern said.

The second study reported in the same issue of the journal followed 120 overweight people for six months. Low-carb dieters dropped an average of 26 pounds, compared to an average of 14 pounds shed by the low-fat group. The low-carb group also had greater decreases in blood fat levels and greater increases in good cholesterol than their counterparts on a low-fat diet.

Unlike other studies, people on the low-carb diet received daily multivitamins and other nutritional supplements like those recommended for people on the Atkins diet. One was an essential-oils supplement containing 1,200 milligrams of fish oil, known for its heart-healthy properties.

"This alone would account for lower triglyceride levels in the low-carb group," noted Katherine Tallmadge, a nutritionist, author, and spokeswoman for the American Dietetic Association. "Why didn't they give the supplements to the low-fat group as well? If they did, that group's triglycerides would have fallen, too."

So what's the bottom line for Americans struggling to trim down? Do these studies vindicate an Atkins-like diet or give critics more reason to vilify the approach?

Since study participants "self-reported" the food they ate and how much physical activity they got, it isn't possible to measure how many calories each group actually consumed and expended, said Tallmadge. "In any case, if they lost more weight, they were eating fewer calories," she concluded.

But in an editorial accompanying the two articles, Dr. Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health, suggested that a low-carb diet may not be a bad way to go.

"We can no longer dismiss very-low-carbohydrate diets," he wrote. Instead of choosing a diet that promises rapid weight loss, people should find a way to eat that they can stick with over time, he said. That may mean experimenting with reduced-carb diets, as long as they emphasize healthy sources of fat and protein and include regular physical activity, he cautioned.

People should see a doctor before starting any diet, particularly if they are taking medications or have other health problems. While a low-carb diet may end up being very good for these types of patients, more study is needed, Yancy said.

Most people, though, can safely cut back on carbohydrates and have beneficial results, Stern noted. "There's no precautions in telling people to cut out soda and french fries, doughnuts, and cookies. There's not a downside to that."

More information

Count your own carbs with the help of the U.S. Department of Agriculture, while the Harvard School of Public Health explains what they are.

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