A year-long, head-to-head study of four widely used diets found that overweight women who followed the very low-carbohydrate Atkins diet had no adverse health effects and lost slightly more weight than women on the other three.

The study by Stanford University researchers compared the Atkins approach with three others: the standard low-fat, reduced-calorie regimen long recommended by many physicians and weight loss experts; the Zone, a reduced-carbohydrate approach developed by author Barry Sears; and the very low-fat, high-carbohydrate regimen created by physician Dean Ornish.

The latest findings add to a growing body of evidence that the very low-carbohydrate, high-protein Atkins diet does not cause the harmful heart and artery effects long feared by many researchers.

Women who followed the Atkins plan had a significant drop in triglycerides, one of the unhealthful blood fats linked to a higher risk of heart disease. Their blood pressure also dropped the most of the four groups, a finding that the researchers think may relate to their slightly greater weight loss. Those in the Atkins group also experienced the largest increase in high-density lipoprotein (HDL), a protective type of cholesterol.

Most importantly, the Atkins group did not develop the soaring levels of low-density lipoprotein (LDL) that some experts have feared might result from eating a diet rich in saturated fat and cholesterol found in fatty cuts of meat, butter and cream. High levels of LDL are a major risk factor for heart disease. The study found that while LDL rose slightly in the Atkins group, their blood levels did not differ statistically from the other three groups.

“This is the best study so far to compare popular diets,” said Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health, because of its size, duration and the small number who dropped out. The findings confirm, he said, that reducing carbohydrates, “especially those with refined starch and sugar like that found in the U.S. diet, has metabolic benefits.” It also shows that replacing these carbohydrates with either fat or protein “can improve blood cholesterol fractions and blood pressure,” he said.

The findings “are pretty much in line with what all the other studies have shown comparing Atkins and low-fat diets,” said Bonnie Brehm, assistant professor of nutrition at the University of Cincinnati College of Nursing and co-author of two, independent studies of the Atkins diet. “We have found the same thing with all of our trials.”

As for weight loss, the goal that concerns dieters the most, none of the groups managed to shed the large numbers of pounds touted by weight-loss programs and television shows such as “The Biggest Loser.”

All the participants reported eating about 2,000 calories a day when the study began. All also reported having cut their intake – some by as much as 500 calories per day at two to six months – but then gradually added back many of those calories. But as researchers noted, if participants truly ate as little as they said, all the groups would have lost much more weight.