Is Low Carb Diets Safe And Effective?

Research on the safety and effectiveness of different diets has been previously limited due to the high number of participants who drop out of studies and because the length of time that the participants are followed is often too short. Researchers at Ben-Gurion University of the Negev in Beer Sheva, Israel, and at Brigham and Women’s Hospital’s (BWH) Channing Laboratory have effectively evaluated three different weight-loss diets over two years and found that both Mediterranean and Low-carbohydrate diets are as effective in achieving weight-loss as low-fat diets.

“The findings suggest that because Mediterranean and low-carbohydrate diets are effective alternatives to low-fat diets, individual preferences could be taken into consideration when tailoring dietary interventions for weight loss,” said Meir Stampfer, MD, DrPH, associate director of the Channing Laboratory at BWH and senior author of the study. The lead author, Dr. Iris Shai of Ben Gurion University, planned the study when she was a Fulbright fellow at Harvard School of Public Health and Channing Laboratory.

Researchers followed 322 obese patients who were randomized to either a low fat, Mediterranean or low-carbohydrate diet for two years. Patients on the low fat and Mediterranean diets were restricted in the number of calories that they could eat, but patients on the low carbohydrate diet were not. Researchers report that after one year, 95 percent of patients had stuck to the diet and after two years, 85 percent had.

After two years, patients in the low fat diet group lost 2.9 kg; patients in the Mediterranean diet group lost 4.4 kg; and patients in the low carbohydrate diet group lost 4.7 kg. The Mediterranean diet-group consumed the highest dietary fiber and monounsaturated to saturated fat ratio. The low-carbohydrate diet-group consumed the fewest carbohydrates and the highest fat, protein and cholesterol. Among all three diet groups, the number of calories consumed was similar. Improvements in other health measures such as liver function and levels of cardiovascular disease were also similar among groups.

In an effort to encourage retention and to enable participants to stick to the diet, the trial was conducted in an isolated workplace at the Nuclear Research Center Negev, Israel, with an on site clinic. Daily diet-group-specific colored food labels were displayed in the cafeteria at the workplace.

The findings suggest that Mediterranean and low-carbohydrate diets are effective alternatives to low fat diets. The more favorable effects on lipids (low-carbohydrate) and on glycemic control (Mediterranean) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions.