For years, the Atkins formula of sparing carbohydrates and loading up on taboo fatty foods has been blasphemy to many in the health establishment, who view it as a formula for cardiovascular ruin.

But now, some of the same researchers who long scoffed at the diet are putting it to the test, and they say the results astonish them. Rather than making cholesterol soar, as they feared, the diet actually appears to improve it, and volunteers take off more weight.

Still, the number of overweight people studied this way is small, and the research does not examine possible long-term ills or advantages, including how long people keep the pounds off.

So for now, the researchers say that much more research is necessary before the Atkins diet can be given an across-the-board endorsement, but at least they believe it is safe enough to take into much larger studies.

At least three formal studies of the Atkins diet have been presented at medical conferences over the past year, and all have reached similar results. The latest, conducted by Dr. Eric Westman of Duke University, was presented Monday at the annual scientific meeting of the American Heart Association, long a stronghold of support for the traditional low-fat approach.

Westman, an internist at Duke's diet and fitness center, said he decided to study the Atkins approach because of concern over so many patients and friends taking it up on their own. He approached the Robert C. Atkins foundation in New York City to finance the research.

Westman studied 120 overweight volunteers, who were randomly assigned to the Atkins diet or the heart association's Step 1 diet, a widely used low-fat approach. On the Atkins diet, people limited their carbs to less than 20 grams a day, and 60% of their calories came from fat.

"It was high fat, off the scale," he said.

After six months, the people on the Atkins diet had lost an average of 31 pounds, compared with 20 pounds on the AHA diet, and more people stuck with the Atkins regimen.

Total cholesterol fell slightly in both groups. However, those on the Atkins diet had an 11% increase in HDL, the good cholesterol, and a 49% drop in triglycerides. On the AHA diet, HDL was unchanged, and triglycerides dropped 22%. High triglycerides may raise the risk of heart disease.

While the volunteers' total amounts of LDL, the bad cholesterol, did not change much on either diet, there was evidence that it had shifted to a form that may be less likely to clog the arteries.

"More study is necessary before such a diet can be recommended," Westman said. "However, a concern about serum lipid (cholesterol) elevations should not impede such research."

No single study is likely to change minds the issue, especially since an initial weight loss is hard to maintain on any diet. Some answers could come from a yearlong study being sponsored by the National Institutes of Health. That experiment, being directed by Dr. Gary Foster of the University of Pennsylvania, will test the Atkins diet on 360 patients.

In the meantime, the heart association's president, Dr. Robert Bonow of Northwestern University, said the organization will reconsider the Atkins diet as more research results become available.

"Having our top academic centers look at this is wonderful," he said. "We are still dealing with small numbers of patients. We just need more data."

Dr. Sidney Smith, the heart association's research director, said it was a surprise that the Atkins diet did not raise LDL cholesterol. "One small study like this flies in the face of so much evidence. We can't change dietary recommendations on the spot," he said.

Dr. Alice Lichtenstein, a nutrition expert at Tufts University, said she thinks too much is made of the amounts of carbohydrates and fats in people's diets as they try to shed weight.

"There is no magic combination of fat versus carbs versus protein," she said. "It doesn't matter in the long run. The bottom line is calories, calories, calories."

Among other reports at the meeting:

• The heart association updated its guidelines on fish consumption, urging people with documented heart disease to eat one serving of oily fish, such as salmon, each day.
• A 12-year follow-up of Harvard's Nurses Health Study found that women who increased their consumption of fruits and vegetables had a 26% lower risk of becoming obese.
• Researchers from the University of Michigan found that older women who are overweight or have had frequent weight swings have impaired blood flow to the heart.