The study conducted by researchers at Ben-Gurion University of the Negev in Beer Sheva, Israel, and at Brigham and Women's Hospital's Channing Laboratory, tracked 322 obese patients for two years and found all three diets were equally safe and effective in providing weight loss benefits.
"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, associate director of the Channing Laboratory at BWH and senior author of the study.
Method
Patients on the low-fat and Mediterranean diets had calorie quotas where as those on low-carb diets did not, conditions that resulted in diet stickability of 95 per cent after one year and 85 per cent after two years, meaning 277 participants completed the trial.
Following conclusion of the trial the low-fat group had lost 3.3kg, the Mediteranean group had lost 4.6kg and the average weight of the low-carb group had dropped by 5.5kg.
The reduction in the ratio of total cholesterol to high-density lipoprotein cholesterol was 20 percent in the low-carbohydrate group and 12 percent in the low-fat group.
The participants had an average age of 52, a Body Mass Index of 31 and were 86 percent male.
The study was conducted at the Nuclear Research Center in Negev, Israel, an isolated workplace that encouraged retention and helped participants stick to the diet.
The Mediterranean group consumed the highest dietary fiber and monounsaturated to saturated fat ratio. The low-carb 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.
The low-fat diet was based on American Heart Association guidelines of energy intake of 1500 kcal per day for women and 1800 kcal per day for men, of which 30 percent of calories were from fat, 10 percent of calories were from saturated fat. 300mg of cholesterol was consumed each day.
The Mediterranean diet had similar calorie input but 35 percent of calories were derived from fat with an emphasis on olive oil and nuts.
The low-carb diet aimed to provide 20g of carbohydrates per day which was gradually increased to close to 120g per day after many months. Low-carbers were directed to choose vegetarian sources of fat and protein and to avoid trans fats.
Conclusions
Researchers noted improvements in liver function and levels of cardiovascular disease were also similar among the various groups and commented:"The increasing improvement in levels of some biomarkers over time up to the 24-month point, despite the achievement of maximum weight loss by 6 months, suggests that a diet with a healthful composition has benefits beyond weight reduction."
They also observed that maximum weight reduction occurred in the first six months, with the following 18 months seeing weight maintenance.
"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," the researchers concluded.
The study was supported by the Nuclear Research Center Negev, The Dr. Robert C. and Veronica Atkins Research Foundation and the S. Daniel Abraham International Center for Health and Nutrition.
Source: New England Journal of Medicine Volume 359, Number3, Pages 229-241 "Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet" Authors: Iris Shai, R.D., Ph.D., Dan Schwarzfuchs, M.D., Yaakov Henkin, M.D., Danit R. Shahar, R.D., Ph.D., Meir Stampfer, MD et al…