In the United States, the prevalence of diabetes mellitus is escalating and it is expected to increase from 5.6% to 12% from the year 2005 to 2050.1 Overnutrition and a sedentary lifestyle increase the risk of type 2 diabetes and contribute to the growing numbers.2 Therefore, therapeutic lifestyle interventions play an important role in delaying diabetes or its complications. Weight loss is associated with decreased insulin resistance and improvements in glycemic control. Currently, the American Diabetes Association recommends calorie restricted low-carbohydrate or low-fat diets for weight loss.3 The Mediterranean diet is a style of eating that is characterized by high consumption of fruits, vegetables, whole grains, beans, nuts and seeds.4 There is low to moderate consumption of dairy products, fish and poultry, with almost no consumption of red meat. Olive oil, a monosaturated fat, is the main source of fat in the Mediterranean diet. Few studies have been conducted comparing the long-term effects of a Mediterranean style diet and low-fat diet in patients with type 2 diabetes.
A recent randomized trial by Esposito et al. compared the effectiveness of a low-carbohydrate Mediterranean-style diet to a low-fat diet in patients with newly diagnosed type 2 diabetes.5 The trial was conducted in a single research center located in Naples, Italy. Overweight, sedentary men and women with type 2 diabetes who were never treated with antihyperglycemic agents and had a hemoglobin A1c (HbA1c) less than 11% were eligible for the study. Exclusion criteria included pregnancy, breastfeeding, use of investigational drugs in last 3 months, use of agents affecting glycemic control, any condition that might compromise adherence to diet regimen, and lab results of elevated liver enzyme levels >3 ULN or Scr >1.4 mg/dL. 215 patients were randomly assigned to either a Mediterranean-style diet (<50% of daily calories from carbohydrates) or low-fat diet (<30% of daily calories from fat). Participants were asked to keep a diet and physical activity log. Adherence to the diets was assessed by session attendance and review of the logs. In addition, participants were also encouraged to increase their physical activity to 30 minutes per day. The primary outcome of the study was time to introduction of antihyperglycemic drug therapy. Secondary outcome measures were changes in weight (including BMI and waist circumference), glycemic control, which was measured by HbA1c, glucose, serum insulin, adiponectin levels, insulin sensitivity and coronary risk factors (lipids and blood pressure). Baseline characteristics were similar between the two treatment groups.
After 4 years, there was a statistically significant difference in the need for antihyperglycemic drug therapy between the two treatment groups; 44% of Mediterranean diet participants versus 70% of low-fat diet participants required treatment (p<0.001). Reductions in weight and BMI were seen in both treatment groups; however the reductions were greater in the Mediterranean diet group compared to the low-fat diet group. In terms of glycemic control, 37% of the participants in the Mediterranean diet group compared to 24% in the low-fat diet group had HbA1c levels less than 7% at the end of 4 years. Overall, participants assigned to the Mediterranean diet group experienced improvements in coronary risk factors compared to the participants assigned to the low-fat diet group. Both treatment groups increased their physical activity; however there was no statistically significant difference in the amount of increase in physical activity between the two treatment groups. Furthermore, there were no statistically significant differences between the use of antihypertensive and lipid lowering agents.
The author’s concluded that the Mediterranean diet delayed the need for antihyperglycemic drug therapy and led to more favorable changes in glycemic control and coronary risk factors in overweight patients with type 2 diabetes. Clinicians may find it challenging to recommend the Mediterranean diet to patients because there is not one specific Mediterranean diet, instead the Mediterranean diet is a more general style of eating that seems to have beneficial outcomes. Therefore, lifestyle modifications should be considered throughout the management of diabetes. More studies are needed to determine the individual effects of the components of a Mediterranean style diet.
1. Marwick T, Hordern M, Miller T, Chyun D, Bertoni A, Blumenthal R, et al. Exercise training for type 2 diabetes mellitus: impact on cardiovascular risk: a scientific statement from the American Heart Association. Circulation
2. Nathan D, Buse J, Davidson M, Ferrannini E, Holman R, Sherwin R, et al. Medical management of hyperglycaemia in type 2 ...