Effects of a Mediterranean-Style Diet on the Need for Antihyperglycemic Drug Therapy in Patients With Newly Diagnosed Type 2 Diabetes: A Randomized Trial

Patients with newly diagnosed type 2 diabetes are usually managed by pharmacotherapy as well as lifestyle changes. The latter are often ineffective and pharmacotherapy may fail over time or may increase cardiovascular and other risks. Specific diets recommended for weight loss in overweight and obese individuals with type 2 diabetes are low-carbohydrate and low-fat calorie-restricted diet. Mediterranean-style diets (MED) have been recommended because they increase insulin sensitivity and improve control of coronary risk factors and hyperglycemia. However, there have been few direct long-term comparisons with other diets in patients with diabetes. This single-center, randomized trial compared the long term effectiveness of a low-carbohydrate MED diet and a low-fat diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes. Effects on glycemic control and coronary risk factors were also compared. The study subjects were 215 overweight individuals, 30 to 70 years of age with newly diagnosed type 2 diabetes, who had a hemoglobin A1c (HbA1c) level <11% and no history of treatment with antihyperglycemic drugs. Participants were randomly assigned to a low-carbohydrate (<50% of daily calories from carbohydrates) MED diet (n = 108) or to a low-fat (<30% of daily calories from fat) diet (n = 107) and were followed for 4 years. Assessors of study outcomes were blinded as to group assignments but participants and the investigators who initiated drug therapy were not. Dietary intake was self-reported. There was a statistically significant difference at the 4-year follow-up in the need for antihyperglycemic drug therapy between patients in the MED group and those in the low-fat group: 44% of patients in the MED diet group and 70% in the low-fat diet group required treatment; the absolute difference was −26.0 percentage points (95% confidence interval [CI], −31.1 to −20.1 percentage points); the hazard ratio was 0.63, with a 95% CI of 0.51 to 0.86. There were essentially no change in the data after adjustment for weight change (hazard ratio, 0.70; 95% CI, 0.59–0.90; P < 0.001). Compared to the low-fat diet group, patients in the MED diet group lost more weight and had greater improvements in glycemic control and coronary risk measures. The investigators conclude from these findings that overweight patients with newly diagnosed type 2 diabetes who use a low-carbohydrate MED diet have improved glycemic control and coronary risk factors, and are more likely to be able to delay the need for oral antihyperglycemic therapy compared to patients using a low-fat diet.