A major new study reveals 3 simple lifestyle changes that can cut the risk of type 2 diabetes by nearly a third.
Adopting a Mediterranean-style diet while also reducing daily calories, engaging in moderate physical activity, and receiving professional weight-loss support may lower the risk of developing type 2 diabetes (T2D) by 31%, according to new research led in part by scientists at the Harvard T.H. Chan School of Public Health.
The findings were recently published in the Annals of Internal Medicine.
“We’re facing a global epidemic of diabetes,” said co-author Frank Hu, Fredrick J. Stare Professor of Nutrition and Epidemiology and chair of the Department of Nutrition. “With the highest-level evidence, our study shows that modest, sustained changes in diet and lifestyle could prevent millions of cases of this disease worldwide.”
Previous studies have associated the Mediterranean diet, which centers on fruits, vegetables, whole grains, and healthy fats, with moderate amounts of dairy and lean proteins and little to no red meat, with improved health outcomes. These benefits include lowering the risk of T2D by improving insulin sensitivity and reducing inflammation.
Researchers working on the PREDIMED-Plus clinical trial, the largest randomized study in Europe to examine diet and lifestyle, set out to determine how the Mediterranean diet’s advantages could be further strengthened by pairing it with additional healthy habits.
Study Design and Participants
The researchers, from 23 universities in Spain and Harvard Chan School, split 4,746 PREDIMED-Plus participants into an intervention group and a control group and followed their health outcomes for six years. The intervention group adhered to a Mediterranean diet; reduced their caloric intake by about 600 calories per day; engaged in moderate physical activity, such as brisk walking and strength and balance exercises; and received professional support for weight loss control.
The control group adhered to a Mediterranean diet without calorie restriction, exercise guidance, or professional support. Participants ranged from age 55 to 75, were overweight or obese, and had metabolic syndrome, but were free of T2D at baseline.
Results and Findings
The study found that those in the intervention group had a 31% lower risk of developing T2D compared to those in the control group. Additionally, the intervention group lost an average of 3.3 kilograms and reduced their waist circumference by 3.6 centimeters, compared to 0.6 kilograms and 0.3 centimeters in the control group.
“In practical terms, 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,” said co-author Miguel Martínez-González, professor at the University of Navarra and adjunct professor of nutrition at Harvard Chan School.
Reference: “Comparison of an Energy-Reduced Mediterranean Diet and Physical Activity Versus an Ad Libitum Mediterranean Diet in the Prevention of Type 2 Diabetes” by Miguel Ruiz-Canela, Dolores Corella, Miguel Ángel Martínez-González, Nancy Babio, J. Alfredo Martínez, Luis Forga, Ángel M. Alonso-Gómez, Julia Wärnberg, Jesús Vioque, Dora Romaguera, José López-Miranda, Ramón Estruch, José Manuel Santos-Lozano, Luis Serra-Majem, Aurora Bueno-Cavanillas, Josep A. Tur, Vicente Martín-Sánchez, Antoni Riera-Mestre, Miguel Delgado-Rodríguez, Pilar Matía-Martín, Josep Vidal, Clotilde Vázquez, Lidia Daimiel, Pilar Buil-Cosiales, Sangeetha Shyam, Jose V. Sorlí, Olga Castañer, Antonio García-Rios, Laura Torres-Collado, Enrique Gómez-Gracia, M. Ángeles Zulet, Jadwiga Konieczna, Rosa Casas, Naomi Cano-Ibáñez, Lucas Tojal-Sierra, Rosa M. Bernal-López, Estefanía Toledo, Jesús García-Gavilán, Rebeca Fernández-Carrión, Albert Goday, Antonio P. Arenas-Larriva, Sandra González-Palacios, Helmut Schröder, Emilio Ros, Montserrat Fitó, Frank B. Hu, Francisco J. Tinahones and Jordi Salas-Salvadó, 25 August 2025, Annals of Internal Medicine.
DOI: 10.7326/ANNALS-25-00388
The study was funded 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 (1R01DK127601).
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