A significant new study has unveiled that making three simple lifestyle changes can reduce the risk of developing type 2 diabetes (T2D) by nearly a third. The research, conducted by scientists at the Harvard T.H. Chan School of Public Health and published in the Annals of Internal Medicine, indicates that adopting a Mediterranean-style diet, reducing daily caloric intake, engaging in moderate physical activity, and receiving professional weight-loss support can lower the risk of T2D by an impressive 31%.
Co-author Frank Hu, a renowned expert and Fredrick J. Stare Professor of Nutrition and Epidemiology at Harvard, emphasized the urgency of addressing this global epidemic of diabetes. “With the highest-level evidence, our study demonstrates that modest, sustained changes in diet and lifestyle could prevent millions of cases of this disease worldwide,” Hu stated.
Previous research has linked the Mediterranean diet—which focuses on fruits, vegetables, whole grains, healthy fats, moderate dairy, lean proteins, and minimal red meat—to improved health outcomes. This dietary pattern is noted for enhancing insulin sensitivity and reducing inflammation, both critical factors in preventing T2D.
The study was part of the PREDIMED-Plus clinical trial, the largest randomized study in Europe focused on diet and lifestyle. The researchers from 23 universities in Spain and the Harvard Chan School enrolled 4,746 participants aged 55 to 75, all of whom were overweight or obese with metabolic syndrome but did not have T2D at the start of the study.
Participants were divided into two groups: an intervention group and a control group. The intervention group followed a strict Mediterranean diet, reduced their caloric intake by approximately 600 calories daily, engaged in moderate physical activities like brisk walking, strength, and balance exercises, and received professional support to manage their weight. In contrast, the control group adhered to the Mediterranean diet without restrictions on caloric intake, exercise guidance, or professional support.
The findings were striking. The intervention group exhibited a 31% lower risk of developing T2D compared to the control group. Moreover, participants in the intervention group lost an average of 3.3 kilograms and reduced their waist circumference by 3.6 centimeters, while the control group saw minimal changes—only 0.6 kilograms and 0.3 centimeters.
Co-author Miguel Martínez-González, a professor at the University of Navarra and adjunct professor of nutrition at Harvard Chan School, highlighted the practical implications: “Adding calorie control and physical activity to the Mediterranean diet prevented around three out of every 100 people from developing diabetes—a clear, measurable benefit for public health.”
The study, a collaborative effort supported by the European Research Council, the Spanish National Institute of Health, the Biomedical Research Networking Centre (CIBER), and the U.S. National Institute of Diabetes and Digestive and Kidney Diseases, paves the way for new strategies in diabetes prevention.
As the diabetes epidemic continues to grow, these findings underscore the importance of lifestyle modifications, specifically through a Mediterranean diet, caloric management, and physical activity. With such evidence at hand, health professionals can better guide patients towards effective prevention strategies against T2D.
For further details, refer to the study titled “Comparison of an Energy-Reduced Mediterranean Diet and Physical Activity Versus an Ad Libitum Mediterranean Diet in the Prevention of Type 2 Diabetes,” published on August 25, 2025, in the Annals of Internal Medicine.
