In a study published in the Journal of the American Medical Association (JAMA) a group of obese and overweight women were assigned to one of four diets—Atkins (low-carb), Zone (30% protein, 40% carbs, 30% fat), Ornish (low-fat) or LEARN (55-60% carbs, less than 10% from saturated fat). Each group followed their assigned diet for one year. During the first two months, they received weekly weight loss tips, and then followed the diets independently for the next ten months. The women who followed Atkins lost the most weight, plus they had the most improvement in their good cholesterol levels, as well as triglycerides, blood glucose, blood pressure, BMI and body fat.
See the study here: www.ncbi.nlm.nih.gov/pubmed/17341711