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A large international clinical trial finds that combining a Mediterranean-style eating pattern with modest calorie reduction, structured physical activity and professional weight-loss support can lower the risk of developing type 2 diabetes (T2D) by about 31% compared with a Mediterranean diet alone. The study, conducted by researchers from 23 Spanish universities in collaboration with investigators at the Harvard T.H. Chan School of Public Health, was published in the Annals of Internal Medicine and tracked nearly 4,800 adults over six years.
A large international study led by Harvard and Spanish researchers suggests that pairing a Mediterranean-style diet with calorie reduction, moderate exercise, and professional support can significantly lower the risk of type 2 diabetes. Credit: Stock
The results provide high-quality randomized evidence that relatively modest, sustained lifestyle changes—rather than extreme diets or intensive medical interventions—can translate into meaningful reductions in diabetes incidence among older adults at elevated metabolic risk.
Study design and participant profile
The trial analyzed data from 4,746 participants enrolled in the PREDIMED-Plus randomized study. All participants were aged roughly 55 to 75, overweight or obese, and presented metabolic syndrome traits (for example, elevated blood pressure, raised fasting glucose, or dyslipidemia), but none had type 2 diabetes at baseline. Investigators randomized participants into two arms:
- Intervention arm: Mediterranean-style diet plus a daily energy deficit of about 600 kilocalories, supervised weight-loss counseling, and a structured program of moderate physical activity (brisk walking and exercises to improve strength and balance).
- Control arm: Mediterranean-style diet alone, without calorie targets, formal exercise prescription, or specialized weight-loss support.
Participants were followed for six years, during which researchers recorded new diagnoses of type 2 diabetes, weight change and waist circumference, among other metabolic outcomes.
Key findings and metabolic outcomes
The combined lifestyle intervention reduced the risk of incident type 2 diabetes by approximately 31% relative to the control group. On average, people in the intervention group lost 3.3 kilograms (about 7.3 pounds) and trimmed their waist circumference by 3.6 centimeters; the control group lost 0.6 kilograms and reduced waist circumference by 0.3 centimeters.
The trial authors note that benefits likely arise from complementary mechanisms: calorie restriction and weight loss improve insulin sensitivity, while Mediterranean-style foods—rich in fruits, vegetables, whole grains, legumes, nuts, and olive oil—reduce systemic inflammation and provide healthier fat profiles. Adding moderate physical activity further augments glucose metabolism and preserves lean muscle, which helps maintain long-term metabolic health.
Co-author Frank Hu, chair of the Department of Nutrition at Harvard Chan School, emphasized the global importance of prevention: sustained, modest changes in diet and activity could translate into millions of prevented cases of diabetes worldwide. Miguel Martínez-González, a senior investigator from the University of Navarra, added that integrating calorie targets and exercise into the Mediterranean dietary pattern produced a measurable public health benefit: roughly three prevented diabetes cases per 100 individuals over the follow-up period.
Implications for prevention and public health
This trial reinforces public-health recommendations that emphasize dietary quality, energy balance and regular physical activity to prevent chronic metabolic disease. Key takeaways for health professionals and the public include:
- Emphasize nutrient-dense, plant-forward meals typical of a Mediterranean diet rather than focusing solely on single nutrients.
- Combine improved diet quality with achievable calorie reduction and regular moderate exercise to increase diabetes prevention efficacy.
- Offer structured counseling and behavioral support to help people adhere to gradual, maintainable changes rather than short-term fixes.
These findings are directly relevant to clinicians designing prevention programs, health systems developing lifestyle medicine services, and policymakers planning population-level interventions to curb the rising burden of T2D.
Expert Insight
Dr. Laura Chen, a public health scientist and science communicator who was not involved in the study, commented: "What makes this trial notable is its scale and real-world approach. The intervention uses accessible ingredients and straightforward activity targets, supported by counseling. That combination—diet quality, modest calorie reduction and behavior support—aligns with what we know about sustainable lifestyle change. For many patients, small, consistent adjustments will yield outsized long-term benefits for metabolic health."
Conclusion
This large randomized trial demonstrates that a Mediterranean-style diet delivers greater protection against type 2 diabetes when paired with daily calorie reduction, routine moderate exercise and professional weight-loss support. The 31% relative risk reduction and modest average weight loss underscore that realistic, sustained lifestyle changes can be powerful tools to prevent diabetes at the population level. For clinicians and health programs, integrating dietary guidance with pragmatic calorie targets, physical activity plans and behavioral counseling offers an evidence-based pathway to reduce future T2D incidence.
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