Eating few grains, fruits or vegetables but plenty of fat-laden meat -- the hallmarks of the controversial diet championed by weight-loss guru Dr. Robert Atkins -- helps dieters shed twice as much weight over the short term and leads to healthier blood-fat levels, according to two studies published today.
The findings, appearing in the New England Journal of Medicine, surprised many researchers who had expected the fatty diet to worsen dieters’ risk factors for heart disease.
“These are important studies,” said Dr. David Ludwig, director of the obesity program at Children’s Hospital Boston. “They will, I think, really dramatically demonstrate that a primary focus on fat reduction may be mistaken.”
The new research, along with another study published last month, is the first controlled trials of at least six months comparing a very low-carbohydrate diet with a conventional, low-fat weight loss strategy. Nutrition experts hailed the studies as long-overdue tests of the hugely popular Atkins diet, and said they are sure to add fuel to the roiling debate over why Americans are getting fatter and how to best slim the nation down.
The authors and other weight loss experts cautioned that the studies were small and relatively short in duration. They said more evidence was needed before a low-carbohydrate weight loss strategy could be recommended.
Some nutritionists say they remain concerned about the possibility of damage to the heart, bones or kidneys caused by increased amounts of saturated fats and protein in such diets.
“Maybe the word on the street is now going to be that this kind of diet appears to be safe -- but we have concerns about the longer-term health risks,” said Dr. Robert Bonow, president of the American Heart Assn., which recommends a conventional, balanced diet rich in fruits and vegetables with limited intake of fats. “Our recommendations are not changing,” Bonow said.
Experts noted that neither the low-carbohydrate diet nor the conventional low-fat diet offered any miracles. The weight loss in both studies was modest.
In one of the studies, led by Dr. Frederick Samaha of the Philadelphia Veterans Affairs Medical Center, participants weighed an average of 288 pounds. By six months, they had lost an average of 13 pounds on the Atkins-style diet and 4 pounds on the conventional diet.
In the second study, led by Gary Foster of the University of Pennsylvania, subjects weighed an average of 216 pounds at the study’s start and by six months had lost an average of 15.4 pounds on the Atkins diet versus 7 pounds on a conventional diet.
After a year, however, there was no statistical difference in weight loss between the two strategies.
The dropout rate was high for both diets -- about 40% in each study.
Rates of obesity have risen sharply in the United States since the 1960s. Nearly two-thirds of American adults are overweight, and more than 30% are obese, according to statistics from the National Centers for Disease Control and Prevention. The increased heft of Americans carries a serious medical toll by increasing rates of heart disease and diabetes.
Among the countless dieting strategies and fads that have emerged over the years, none has been more popular than that of Atkins, who died last month after a fall on an icy sidewalk.
In the Atkins diet, first published in 1972, intake of carbohydrates is slashed but dieters may eat as much meat and fat as they like. A typical Atkins breakfast: a plate of bacon. An Atkins no-no: a bowl of cereal and glass of orange juice.
Atkins believed that such a regimen worked because it put the body into a state known as “ketosis” that caused fat to melt more efficiently from the body.
Some nutritionists have suspected that the Atkins diet actually works for other reasons. Such diets often contain proportionally more protein, which satisfies appetites more effectively than sugars and starch. An Atkins-style diet also offers far fewer choices than does a conventional diet, and a lack of variety simply makes people eat less.
Foster, the lead author of the one-year study, said he always dismissed the Atkins diet but felt it was important to study it because it is so popular.
“Here’s a diet that has sold 10 million books at least,” he said. “How was it that we have a long-standing and popular approach to weight management that had never been evaluated in a randomized controlled trial?”
Foster’s study, conducted jointly by scientists at the University of Pennsylvania, the University of Colorado and Washington University in St. Louis, enrolled 63 moderately obese participants -- 43 women and 20 men.
At the start of the study, participants were randomly assigned to receive a copy of either “Dr. Atkins’ New Diet Revolution” or “The LEARN Program for Weight Management,” which offers a conventional low-fat weight loss approach. Both groups were instructed to follow their assigned book’s advice.
In addition to the differences in weight loss, periodic blood samples revealed a significant difference in blood lipids associated with heart disease risk. The Atkins diet group showed higher levels of HDL, or “good,” cholesterol and lower levels of triglycerides, which are fatty substances linked to heart disease.
The other study enrolled 132 severely obese men and women, 39% of whom were diabetic and 43% of whom had a metabolic syndrome that put them at high risk for diabetes and heart disease. The subjects had regular contact with nutritional counselors and were assigned a conventional or low-carbohydrate, Atkins-like diet.
Again, the low-carbohydrate group showed greater improvements in triglyceride levels. Diabetics also improved in their ability to control blood-sugar levels.
The two studies are in agreement with another study published last month that found that 53 overweight women following an Atkins-style diet lost, on average, twice as much weight (18.5 pounds ) than did those adopting a conventional low-fat approach (8.5 pounds).
Despite the weight loss, Barbara Rolls, a professor of nutrition at Pennsylvania State University in University Park, said the findings should not be considered a green light for the Atkins diet.
She noted that after 12 months the Atkins group had regained more weight than the people on a conventional diet.
“We need to work with people to help them figure out what kind of eating habits they can sustain and that are healthy,” Rolls said. “We haven’t done so with this, that’s for sure.”