Headed by Dr. Iris Shai, the study intensively monitored 322 moderately obese people, who were randomly assigned one of three diets: a low-fat, calorie-restricted diet; a Mediterranean calorie-restricted diet with the highest level of dietary fiber and monounsaturated/saturated fat; or a low-carbohydrate diet with the least amount of carbohydrates, highest fat, protein, and dietary cholesterol. The low-carb dieters had no caloric intake restrictions.
While the participants actually decreased their total daily calories consumed by a similar amount, but still the net weight loss from the low-fat diet after two years was only 6.5 lbs. (2.9 kg) compared to 10 lbs. (4.4 kg) on the Mediterranean diet, and 10.3 lbs. (4.7 kg) on the low-carbohydrate diet.
"These weight reduction rates are comparable to results from physician-prescribed weight loss medications," explained Shai.
The researchers noted that the low-fat diet reduced the total cholesterol to HDL ratio by only 12 percent, while the low-carbohydrate diet improved the same ratio by 20 percent. Lipids improved the most in the low-carbohydrate, with a 20 percent increase in the HDL ("good") cholesterol and, 14 percent decrease in triglycerides. In all three diets, inflammatory and liver function biomarkers was equally improved.
But, in diabetic participants, the standard low-fat diet actually increased the fasting glucose levels by 12mg/dL, while the Mediterranean diet induced a decrease in fasting glucose levels by 33mg/dL.
The study also holds significance because of the relatively large number of participants coupled with a low drop-out rate - 95 percent were in the study after one year and 85 percent were still participating after the second.
"Clearly, there is not one diet that is ideal for everyone. We believe that this study will open clinical medicine to considering low-carb and Mediterranean diets as safe effective alternatives for patients, based on personal preference and the medical goals set for such intervention. Furthermore, the improvement in levels of some biomarkers continued until the 24-month point, although maximum weight loss was achieved by 6 months. This suggests that healthy diet has beneficial effects beyond weight loss," concluded Shai.
The study was published in the prestigious New England Journal of Medicine.