Scientific Study

BACKGROUND: Low-carbohydrate and low-fat calorie-restricted diets are recommended for weight loss in overweight and obese people with type 2 diabetes. OBJECTIVE: To compare the effects of a low-carbohydrate Mediterranean-style or a low-fat diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes. DESIGN: Single-center; randomized trial. Randomization was computer-generated and unstratified. Allocation was concealed in sealed study folders held in a central; secure location until participants gave informed consent. Participants and investigators were aware of treatment assignment; and assessors of the primary outcome were blinded. SETTING: Teaching hospital in Naples; Italy. PATIENTS: 215 overweight people with newly diagnosed type 2 diabetes who were never treated with antihyperglycemic drugs and had hemoglobin A(1c) (HbA(1c)) levels less than 11%. INTERVENTION: Mediterranean-style diet (<50% of daily calories from carbohydrates) (n = 108) or a low-fat diet (<30% of daily calories from fat) (n = 107). MEASUREMENTS: Start of antihyperglycemic drug therapy; defined by protocol as indicated for follow-up HbA(1c) level greater than 7% (primary outcome); and changes in weight; glycemic control; and coronary risk factors (secondary outcomes). RESULTS: After 4 years; 44% of patients in the Mediterranean-style diet group and 70% in the low-fat diet group required treatment (absolute difference; -26.0 percentage points [95% CI; -31.1 to -20.1 percentage points]; hazard ratio; 0.63 [CI; 0.51 to 0.86]; hazard ratio adjusted for weight change; 0.70 [CI; 0.59 to 0.90]; P < 0.001). Participants assigned to the Mediterranean-style diet lost more weight and experienced greater improvements in some glycemic control and coronary risk measures than did those assigned to the low-fat diet. LIMITATIONS: Investigators responsible for initiating drug therapy were not blinded to treatment assignment. Dietary intake was self-reported. CONCLUSION: Compared with a low-fat diet; a low-carbohydrate; Mediterranean-style diet led to more favorable changes in glycemic control and coronary risk factors and delayed the need for antihyperglycemic drug therapy in overweight patients with newly diagnosed type 2 diabetes.