BGU Study Fuels Low-Fat vs. Low-Carb Debate
August 3, 2008
Overweight people on low-carbohydrate and Mediterranean diets lost more weight and got greater cardiovascular benefits than people on a conventional low-fat diet, according to a study that endorses alternative diets published in a major medical journal.
The study, which tracked 322 Israelis for two years, surprisingly found that a low-carb diet, often associated in the U.S. with high levels of meat consumption — was better than a low-fat diet in boosting blood levels of “good” cholesterol, or high-density lipoproteins associated with cardiovascular health benefits. It also determined that the Mediterranean diet, which includes wine, olive oil, whole grains and fruits, was better than the low-fat diet in controlling glucose levels.
The researchers suggested that doctors and nutritionists could use the findings to tailor diets individually to patients with heart disease or diabetes, stressing that these were alternatives to low-fat diets that many people find hard to follow. The results also indicated that worries that low-carb diets, in particular, might cause health problems, are unfounded.
“A lot of people believe a low-fat diet is the only sanctioned weight-loss diet,” said Meir J. Stampfer, an epidemiology and nutrition professor at the Harvard School of Public Health who was senior author of the report, published in Thursday’s edition of the New England Journal of Medicine. The study found that “there are alternatives that work better.”
The study’s leader, Iris Shai of Ben-Gurion University of the Negev, said, “We believe that this study will open clinical medicine to considering low-carb and Mediterranean diets as safe, effective alternatives for patients.”
The study was funded with a $497,000 grant from the Jenkintown, Pa., nutritional-research foundation established by Robert Atkins, the late diet guru whose Atkins diet is controversial because it allows dieters to consume large amounts of meat and cheese, while eliminating bread and pasta. The foundation said it didn’t influence the findings, and the study’s authors said they didn’t have any financial conflicts under the New England Journal guidelines.
Dean Ornish, a doctor and University of California at San Francisco professor who advocates extremely low-fat diets, said the Israel study shouldn’t be seen as endorsement of the Atkins diet because the low-carb participants in the study were encouraged to consume vegetable fats, as opposed to the meat fats that Atkins dieters typically ingest. “A vegetarian Atkins diet is almost an oxymoron,” he said. He also said the low-fat diet in the study, which was based on recommendations by the American Heart Association, doesn’t cut out enough fat.
Low-carb diet advocates said they weren’t surprised by the results, which they said confirm shorter, smaller, studies done over the past 20 years. Last March, Stanford University researchers reported in the Journal of the American Medical Association that over the course of a year, overweight women assigned to follow the Atkins diet lost an average of 10 pounds, exceeding losses recorded by women on other diets in the study. However, the study was criticized because many of the women didn’t stick with diet guidelines and because they were paid to participate.
Stephen Phinney, professor emeritus of nutrition at University of California at Davis who has researched high-protein, low-carb diets for more than 25 years, said that with publication in the New England Journal — which he called “the keeper of the consensus in medicine” — he expects that “what was considered unacceptable, becomes mainstream thought.”
Jimmy Moore, a 36-year-old from Spartanburg, S.C., who operates a dieter’s Web site, says he lost 180 lbs. after going on the Atkins diet four years ago. He said he did it even though his doctor “thought I was nuts.” He says his doctor was impressed with his diet success, and publication of the study may convince him to recommend the diet to other overweight patients.
In the Israel study, after two years, those in the group assigned to the low-carb diet lost an average of 10.3 lbs. — 58% more than the 6.5 lbs. lost by dieters who followed the low-fat diet based on the Heart Association recommendations. Those on the Mediterranean diet, which includes lots of carbohydrates like pasta and more calories from fat in the form of olive oil than the Heart Association recommends, lost 10 lbs., nearly as much as the low-carb diet.
Excluding drop-outs, the average weight loss was 12.3 lbs. for the low-carb dieters, 10.2 lbs. for the Mediterranean dieters and 7.3 lbs. for the low-fat dieters. The subjects started out with an average body-mass index of 31, well above the top level of 24.9 considered normal weight. About 85% of those in the study were men.
The study was conducted among a group of workers at Israel’s Nuclear Research Center in Dimona. Aided by support from the center, including color-coded menu information in the company cafeteria, 95% of the employees stuck with their diets for a full year and 85% were still involved at the end of the two-year study. Dr. Shai, the lead researcher, said that the “support in the workplace,” helped people stay on the diets, even after weight loss plateaued at the six-month mark. She said the success suggests that workplace support for diet programs could help employers improve employee health.
The low-carb diet was also found to reduce harmful triglycerides, a precursor of heart disease, more than the low-fat diet. Levels of “bad” cholesterol, or low-density lipoprotein, which is associated with the formation of arterial blockages, didn’t significantly differ among the three diets.
Low-carb diets permit people to freely eat cheese, meats and animal fats that are discouraged in traditional diets, although in the Israel study, employees were counseled to emphasize vegetable fats. The low-carb dieters weren’t given any restrictions on the number of calories they could consume, although they ended up eating about the same number of calories as the other two groups, indicating that they were satiated by their fat consumption. After an initial two-month period with just 20 grams a day of carbohydrates, they were allowed to consume up to 120 grams a day, well above the Atkins-recommended levels.
The low-fat and Mediterranean dieters were restricted to 1,800 calories a day for men and 1,500 for women. The Mediterranean dieters were urged to eat poultry and fish instead of beef and lamb, and they ate a handful of tree nuts and about five tablespoons of olive oil a day, so they got 35% of calories from fat. The low-fat dieters got just 30% of calories from fat.
Dr. Shai, the study leader, said she conceived the study when she was at Harvard School of Public Health in Boston on a Fulbright scholarship. “Before I came, I had the understanding that a low-fat diet was the best. But after I came, I started to think maybe we are wrong.” Dr. Shai, 39 years old, said she thought the Israel nuclear research center would be a good place to run a study because it is isolated and people seldom leave. In addition, people were all on a private computer network, making it easy to monitor employee compliance by administering electronic questionnaires. But she says, “The main effects could be achieved in any workplace.”
Barbara Howard, former chairwoman of the American Heart Association’s Council on Nutrition, said that the group hasn’t advocated a low-fat diet in recent years. She said reducing total calories and exercise are the key to weight loss. The group also urges people to avoid saturated fats and limit “calorie dense foods” such as fats and “highly processed carbs like pastries.”