BOSTON — In a development with dark echoes of the early 2000s, a study published July 17 in the New England Journal of Medicine found that participants in a two-year study lost more weight on a low-carbohydrate diet than on a Mediterranean or low-fat diet.
While rectifying a number of flaws of earlier studies, including short duration and high attrition rates, the study, conducted in a workplace at a research center in Dimona, Israel, has attracted skepticism over a number of issues, beginning with the design of the low-carbohydrate diet (meat intake was discouraged) and over the principal source of its funding — the Dr. Robert C. and Veronica Atkins Research Foundation. The study was launched in December 2004, 20 months after the death of Dr. Atkins, the most famous proponent of low-carbohydrate dieting.
Weight loss was the study’s primary aim, and participants on the low-carbohydrate diet lost an average of 10.3 lbs after two years, slightly more weight than those in the Mediterranean diet (10 lbs) and significantly more than those on what the study referred to as a low-fat diet (6.5 lbs). Weight loss was greatest in the first several months on all three diets. Subjects gained back some of the lost weight on all three diets but their weight leveled off during the final six months or so.
Participants in the study were counseled at regular intervals about their diets and ate lunch each day at a workplace cafeteria where food selections were adjusted and labeled to help participants comply with their dietary regimens. For subjects following the low-fat and Mediterranean diets, caloric intake was limited. For the low-carbohydrate diet, it was not. Lunch is the main meal of the day in Israel.
"Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets," said the authors of the study, "Weight Loss with a Low-Carbohydrate, Mediterranean or Low-Fat Diet." The study was written by a team led by Iris Shai from the S. Daniel Abraham Center for Health and Nutrition at Ben-Gurion University of the Negev in Be’er-Sheva, Israel. Other researchers participating in the study were from the University of Leipzig in Germany and Brigham and Women’s Hospital and Harvard Medical School, and the departments of Epidemiology and Nutrition at the Harvard School of Public Health.
While the researchers said the low-carbohydrate diet was "based on the Atkins diet," they said participants were "counseled to choose vegetarian sources of fat and protein and to avoid trans fat."
The other diets limited daily caloric intake to 1,500 for women and 1,800 for men. The Mediterranean diet limited fat intake to 35% of calories while the low-fat diet limited fat to 30%.
Judi Adams, president of the Grain Foods Foundation, raised questions about how effectively the low-fat diet participants may have been counseled.
"It is important to note that those subjects who followed the low-fat diet decreased their fiber intake despite being ‘counseled to consume low-fat grains, vegetables, fruits and legumes,’ all of which contain fiber," she said. "This calls into question how closely the low-fat diet was followed, and since fiber is linked to weight control, the low-fat diet in this study is less than optimal."
Marcia Scheideman, president of the Wheat Foods Council, suggested that a low-fat diet in which 30% of caloric intake was fat "wasn’t really low in fat." Ms. Scheideman also said the "very structured group" participating in the study was unrealistic versus what is possible in the real world.
The American Heart Association was unmoved by the study’s findings.
"The American Heart Association doesn’t recommend high-protein diets for weight loss," the association said in response to the study. "Some of these diets restrict healthful foods that provide essential nutrients and don’t provide the variety of foods needed to adequately meet nutritional needs. People who stay on these diets very long may not get enough vitamins and minerals and face other potential health risks."
Looking at sub groups among participants, low-carbohydrate dieters did not always achieve the best results. For instance, among the 45 women in the study, the Mediterranean diet yielded the greatest weight loss. Among 36 participants who were diabetic, only the Mediterranean diet lowered blood sugar levels.
The authors of the study suggested their findings should challenge tendencies of health professionals to be dismissive toward low-carbohydrate dieting.
"Our results suggest that health care professionals might consider more than one dietary approach, according to individual preferences and metabolic needs, as long as the effort is sustained," they said. MBN