Comparison of an Energy-Reduced Mediterranean Diet and Physical Activity Versus an Ad Libitum Mediterranean Diet in the Prevention of Type 2 Diabetes : A Secondary Analysis of a Randomized Controlled Trial

Abstract

Background: Limited research has been done to evaluate the combined effect of energy reduction, Mediterranean diet (MedDiet), and physical activity on type 2 diabetes incidence.

Objective: To evaluate whether an energy-reduced MedDiet (erMedDiet) plus physical activity reduces diabetes incidence compared with a standard MedDiet.

Design: Prespecified secondary outcome analysis in the PREDIMED (Prevención con Dieta Mediterránea)-Plus randomized, single-blinded, controlled trial. (ISRCTN Registry: ISRCTN89898870).

Setting: 23 centers across Spain.

Participants: 4746 adults aged 55 to 75 years with metabolic syndrome and overweight or obesity, without prior cardiovascular disease or diabetes.

Intervention: Participants were randomly assigned 1:1 to an intervention group receiving an erMedDiet (planned reduction of 600 kcal per day), increased physical activity, and behavioral strategies for reducing weight, or a control group receiving ad libitum MedDiet advice.

Measurements: Diabetes incidence was based on the American Diabetes Association criteria. Anthropometric measurements were obtained annually. Cox regression models were used to assess the intervention effect.

Results: The 6-year absolute risk was 12.0% (95% CI, 11.9% to 12.1%) in the control group (349 cases) and 9.5% (CI, 9.4% to 9.5%) in the intervention group (280 cases). Over a median 6-year follow-up, diabetes incidence was 31% (CI, 18% to 41%) relatively lower in the intervention group compared with the control group, with an absolute risk reduction of -2.6 cases (CI, -2.7 to -2.4) per 1000 person-years. The intervention group attained better adherence to the erMedDiet, higher physical activity levels, and greater reductions in body weight and waist circumference.

Limitation: Secondary outcome, single-blinded design, and self-reported dietary adherence.

Conclusion: An intensive intervention with the MedDiet adding caloric reduction, physical activity, and modest weight loss was more effective than only an ad libitum MedDiet in reducing diabetes incidence in overweight/obese persons with metabolic syndrome.

Primary funding source: Instituto de Salud Carlos III.