Frank Hu, MD, PhD | Image Credit: Menus of Change
When combined with a Mediterranean diet, calorie reduction and moderate exercise may cause up to a 1/3 reduction in type 2 diabetes (T2D) risk, according to recent research.1
The Mediterranean diet has historically been connected to better health outcomes via improved insulin sensitivity and reduced inflammation. The diet primarily consists of a high intake of fruits, vegetables, whole grains, and healthy fats, with a moderate amount of dairy and lean proteins, and little to no red meats.1
Previous research, such as a trial from the University of Granada in 2020, which examined over 100,000 individuals via a structured literature search, has linked the Mediterranean diet with T2D incidence specifically. These studies frequently connect adherence to the diet and significant decreases in T2D risk – the University of Granada study saw a reduction of roughly 20% among those with a high score on the Mediterranean Diet Adherence Questionnaire.3
“We’re facing a global epidemic of diabetes,” co-author Frank Hu, MD, PhD, Frederick J. State Professor of Nutrition and Epidemiology and chair of the Department of Nutrition, said in a statement to Eurekalert. “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.”1
Conducted by researchers from the Harvard TH Chan School of Public Health, this study examined 4746 PREDIMED-Plus participants. Investigators randomly assigned these participants in a 1:1 ratio to either an intervention or a control group and followed their health outcomes over 6 years. Ages ranged from 55 to 75 years, and patients were overweight or obese and had metabolic syndrome. However, all participants were free of T2D and cardiovascular disease at baseline.1,2
The intervention group kept to a strictly Mediterranean diet, reduced their caloric intake by roughly 600 calories/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 any caloric restrictions, exercise guidance, or professional support.1
Investigators reported a 6-year risk of 12% (95% CI, 11.9% to 12.1%) in the control group (349 cases) and 9.5% (95% CI, 9.4% to 9.5%) in the intervention group (280 cases). During the 6-year follow-up, T2D incidence was 31% (95% CI, 18% to 41%) lower in the intervention group compared to control, with an average risk reduction of -2.6 cases (95% CI, -2.7 to -2.4) per 1000 person-years.2
Additionally, participants in the intervention group lost an average of 3.3 kilograms and reduced waist circumference by an average of 3.6 centimeters, compared to 0.6 kilograms and 0.3 centimeters in the control group.1
“In practical terms, adding calorie control and physical activity to the Mediterranean diet prevented around 3 out of every 100 people from developing diabetes—a clear, measurable benefit for public health,” said co-author Miguel Martinez-Gonzalez, PharmD, PhD, professor at the University of Navarra and adjunct professor of nutrition at Harvard Chan School.1
References
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Harvard TH Chan School of Public Health. Mediterranean diet combined with calorie reduction and exercise may reduce risk of type 2 diabetes by nearly one-third. Eurekalert! August 25, 2025. Accessed August 28, 2025. https://www.eurekalert.org/news-releases/1095532
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Ruiz-Canela M, Corella D, Martínez-González MÁ, et al. 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. Ann Intern Med. Published online August 26, 2025. doi:10.7326/ANNALS-25-00388
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Martín-Peláez S, Fito M, Castaner O. Mediterranean Diet Effects on Type 2 Diabetes Prevention, Disease Progression, and Related Mechanisms. A Review. Nutrients. 2020;12(8):2236. Published 2020 Jul 27. doi:10.3390/nu12082236