Atkins Fares Best in Study Of Four Weight-Loss Regimens
Wednesday, March 7, 2007
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 Dean Ornish.
The latest findings add to a growing body of evidence that the 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 important, the Atkins group did not develop the soaring levels of low-density lipoprotein (LDL) that some experts have thought 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 for those in the Atkins group, their blood levels did not differ statistically from the other groups.
"This is the best study so far to compare popular diets," said Walter Willett, chair 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 adding back many of those calories. But as researchers noted, if participants ate as little as they said, all the groups would have lost much more weight.
At first, the Atkins group lost weight faster. But as in previous studies, the pounds shed began to even out across the four groups. After a year, women in the Atkins group averaged a modest 10-pound loss compared with about six pounds for those in the other groups.
Both the authors and other weight-loss experts were quick to note that the new findings did not answer the question of what is the best way for most people to shed weight.
"This isn't a study testing how well you would do if you followed these diets to the letter," notes Christopher Gardner, assistant professor of medicine at the Stanford Prevention Research Center and lead author of the study, which appears in tomorrow's Journal of the American Medical Association. "This is a study that shows what happens if you bought the book and tried to follow" the diets, as most dieters do.
The 311 overweight and obese women in the study were randomly assigned to one of the four groups. Each received a book detailing her prescribed diet. For the first eight weeks, the women also attended one-hour weekly group sessions with a registered dietitian trained to explain the diet in detail. Participants received follow-up phone calls and e-mails to remind them of appointments, and they were paid $25 to $75 for each appointment they made.
Reactions to the findings were mixed.
"It's bad science, good publicity," said the Zone's Sears.
"For all practical purposes, the programs all worked about the same," said Kelly D. Brownell, director of Yale University's Rudd Center for Food Policy and Obesity and creator of the Lifestyle, Exercise, Attitudes, Relationships and Nutrition (LEARN) program for weight management, one of the diets studied. The extra four pounds lost by the Atkins group are not very meaningful, Brownell said.
Others were more critical.
"This study is seriously flawed, and its conclusions misleading," said Ornish, clinical professor of medicine at the University of California at San Francisco. A careful read of the study shows "no significant difference in weight loss between the Atkins and Ornish or LEARN diets after one year!" he noted in an e-mail. "There was significantly more weight loss on the Atkins diet after one year only when compared with the Zone diet. This directly contradicts their primary conclusion."
All low-carbohydrate diets are not necessarily created equal, however. A study last year by Willett and his colleagues in the New England Journal of Medicine found that women on low-carb diets who ate mostly animal fat and animal protein did not reduce their risk of heart disease. But those who ate vegetable forms of protein, such as soy, and fat, such as olive oil, did reduce their risk of heart disease. As Willett said yesterday, "lower-carbohydrate diets look like a good option, but if you consider them, eat olive oil and fish rather than butter and sausage."