The Atkins diet may have proved itself after all: A low-carb diet and a Mediterranean-style regimen helped people lose more weight than a traditional low-fat diet in one of the largest studies to compare the dueling weight-loss techniques.
A bigger surprise: The low-carb diet improved cholesterol more than the other two. Some critics had predicted the opposite.
“It is a vindication,” said Abby Bloch of the Dr. Robert C. and Veronica Atkins Foundation, a philanthropy group that honors the Atkins diet's creator and was the study's main funder.
However, all three approaches – the low-carb diet, a low-fat diet and a so-called Mediterranean diet – achieved weight loss and improved cholesterol.
The study is remarkable not only because it lasted two years, much longer than most, but also because of the huge proportion of people who stuck with the diets – 85 percent.
Researchers approached the Atkins Foundation with the idea for the study. But the foundation played no role in the study's design or results, said the lead author, Iris Shai of Ben-Gurion University of the Negev.
Other experts said the study – being published today in the New England Journal of Medicine – was highly credible.
“This is a very good group of researchers,” said Kelly Brownell, director of Yale University's Rudd Center for Food Policy and Obesity.
The research was done in a controlled environment – an isolated nuclear research facility in Israel. The 322 participants got their main meal of the day, lunch, at a central cafeteria.
In the cafeteria, the appropriate foods for each diet were identified with colored dots, using red for low-fat, green for Mediterranean and blue for low-carb.
As for breakfast and dinner, the dieters were counseled on how to stick to their eating plans and were asked to fill out questionnaires on what they ate.
The low-fat diet – no more than 30 percent of calories from fat – restricted calories and cholesterol and focused on low-fat grains, vegetables and fruits as options. The Mediterranean diet had similar calorie, fat and cholesterol restrictions, emphasizing poultry, fish, olive oil and nuts.
The low-carb diet set limits for carbohydrates, but none for calories or fat. It urged dieters to choose vegetarian sources of fat and protein.
Average weight loss for those in the low-carb group was 10.3 pounds after two years. Those in the Mediterranean diet lost 10 pounds, and those on the low-fat regimen dropped 6.5.
More surprising were the measures of cholesterol. Critics have long acknowledged that an Atkins-style diet could help people lose weight but feared that over the long term, it may drive up cholesterol because it allows more fat.