Briefing: Diet, Exercise and Type 2 Diabetes Prevention
Date: 25 August 2025

Source: Excerpts from "Diet, Exercise and Type 2 Diabetes," a study led by Miguel Ruiz-Canela, PhD, and Dolores Corella, PhD, Instituto de Salud Carlos III, Madrid, Spain, published online in Annals of Internal Medicine.

TOPLINE: Combining caloric restriction and physical activity with a Mediterranean diet significantly reduces the risk of developing type 2 diabetes (T2D) by 31% in adults with overweight or obesity and metabolic syndrome, compared to following a Mediterranean diet alone. This suggests a more proactive approach beyond simply adhering to the traditional Mediterranean diet.

MAIN THEMES AND IMPORTANT IDEAS/FACTS:

Enhanced Diabetes Prevention through Multi-faceted Intervention:
The core finding is that "adding caloric restriction and physical activity to a Mediterranean diet reduced the risk of developing type 2 diabetes (T2D) by 31% compared with following a Mediterranean diet alone."
This builds upon previous research, specifically the PREDIMED trial, which showed that while an ad libitum Mediterranean diet reduced diabetes incidence, it achieved "only minimal weight loss." The PREDIMED-Plus trial aimed to address this by incorporating "an energy-reduced Mediterranean diet combined with physical activity and dietitian-led behavioral support."
Study Methodology and Design:
The PREDIMED-Plus trial, from which this secondary analysis was derived, involved 4746 adults (mean age 64.9 years, 50% women) with metabolic syndrome and overweight or obesity, who were T2D-free at baseline.
Participants were randomly assigned to one of two groups:
Intervention Group (n = 2342): Received an "energy-reduced Mediterranean diet (600 kcal/d reduction) with physical activity recommendations and behavioral support."
Control Group (n = 2404): Received "educational sessions on the traditional Mediterranean diet with ad libitum caloric intake."
Crucially, "all the participants received 1 L of extra-virgin olive oil monthly to support adherence," indicating a commitment to the Mediterranean dietary framework across both groups.
T2D incidence was tracked annually over a 7-year period (6 years intervention + 1 observation year) using American Diabetes Association criteria.
Significant Outcomes and Risk Reduction:
Over a median follow-up of 6.6 years, "diabetes was diagnosed in 629 participants."
Incidence rates were notably lower in the intervention group: "18.7 vs 23.2 cases per 1000 person-years in the intervention vs control group."
The intervention group demonstrated a "31% lower relative risk for incident diabetes than those in the control group, with an adjusted absolute risk reduction of 2.4%."
An interesting nuance is that "the risk reduction was more prominent in men than women."
Broader Health Benefits and Adherence:
Beyond diabetes prevention, the intervention group also showed "better adherence to the energy-reduced Mediterranean diet, higher physical activity levels, and greater reductions in body weight and waist circumference than the control group." These are important indicators of overall health improvement and compliance.
Clinical Recommendations and Practical Application:
The authors advocate for this integrated approach in clinical practice, stating: "Clinicians should consider recommending this approach for patients with overweight or obesity, particularly when conventional Mediterranean dietary advice alone has proven insufficient."
They also highlight the Mediterranean diet's inherent advantages: "Although there is no ‘one-size-fits-all’ dietary strategy plan for diabetes prevention, the MedDiet’s higher palatability and cultural acceptance could make it a highly sustainable, long-term, weight-loss option when combined with moderately reduced energy intake.”
LIMITATIONS: It's important to note that diabetes was a secondary outcome of the PREDIMED-Plus trial. Dietary adherence was self-reported, which introduces a potential for bias. Furthermore, the findings "may have limited generalizability beyond adults aged 55-75 years with metabolic syndrome in a European Mediterranean country." This suggests the need for further research in diverse populations.