Mediterranean diet combined with calorie reduction and exercise lowers diabetes risk by 31%

Eating Mediterranean-style, but with fewer calories, moderate exercise and professional support for weight loss, reduces the risk of developing type 2 diabetes by 31%. This is the main finding of PREDIMED-Plus, a large Spanish clinical trial in which the University of Navarra participates, in collaboration with more than 200 researchers from 22 universities, hospitals, and research centres in Spain. It has been conducted in over 100 primary care centres of the Spanish National Health System.

The study, the largest nutrition trial ever conducted in Europe, began in 2013 with funding of more than €2 million from a European Research Council (ERC) Advanced Grant. Subsequently, between 2014 and 2016, other institutions joined the trial, bringing overall funding to more than €15 million, provided mainly by the Carlos III Health Institute (ISCIII) and the Center for Biomedical Research Network (CIBER) through its areas of Physiopathology of Obesity and Nutrition (CIBEROBN), Epidemiology and Public Health (CIBERESP), and Diabetes and Associated Metabolic Diseases (CIBERDEM).

The study, published in Annals of Internal Medicine, followed 4,746 people aged 55 to 75 years with overweight or obesity and metabolic syndrome, with no history of cardiovascular disease or diabetes, for six years. To evaluate whether an optimised version of the Mediterranean diet could reinforce the prevention of type 2 diabetes, researchers compared two groups: one adopted a calorie-reduced Mediterranean diet (about 600 kcal fewer per day), a moderate exercise plan (brisk walking, strength and balance training), and professional guidance. The other followed the traditional Mediterranean diet, without calorie restriction or exercise advice.

Results show that, beyond reducing diabetes risk, the intervention group lost an average of 3.3 kg and reduced waist circumference by 3.6 cm, compared to just 0.6 kg and 0.3 cm in the control group. In practical terms, this meant preventing approximately three in every 100 participants from developing type 2 diabetes — a significant public health benefit.

‘Diabetes is the first solid clinical outcome for which we have shown — using the strongest available evidence — that the Mediterranean diet with calorie reduction, physical activity and weight loss is a highly effective preventive tool,’ said Miguel Ángel Martínez-González, Professor of Preventive Medicine and Public Health at the University of Navarra, Adjunct Professor of Nutrition at Harvard University, and principal investigator of the project.

‘Applied at scale in at-risk populations, these modest and sustained lifestyle changes could prevent thousands of new diagnoses every year. We hope soon to show similar evidence for other major public health challenges.’

Type 2 diabetes now affects more than 530 million people worldwide, according to the latest data from the International Diabetes Federation. Its rapid growth is driven by urbanisation (unhealthy diets, sedentary lifestyles, reduced physical activity), an ageing population, and rising rates of overweight and obesity. In Spain, where some 4.7 million adults live with diabetes (most of them type 2), the disease has one of the highest rates in Europe, which overall has more than 65 million people with diabetes. In the United States, the figure is approximately 38.5 million, and the prevalence far exceeds the global average, with one of the highest healthcare costs per patient worldwide. Experts warn that prevention is essential to curb this public health emergency, which significantly increases the risk of cardiovascular, renal, and metabolic complications.

‘The Mediterranean diet acts synergistically to improve insulin sensitivity and reduce inflammation. With PREDIMED-Plus, we demonstrate that combining calorie control and physical activity enhances these benefits,’ explained Miguel Ruiz-Canela, Professor and Chair of the Department of Preventive Medicine and Public Health at the University of Navarra’s School of Medicine and first author of the study.

‘It is a tasty, sustainable and culturally accepted approach that offers a practical and effective way to prevent type 2 diabetes — a global disease that is, to a large extent, avoidable.’

The PREDIMED-Plus project (2013-2024), which involves different patients, is a continuation of the PREDIMED study (2003-2010). This study demonstrated that following a Mediterranean diet enriched with extra-virgin olive oil or nuts reduces the risk of cardiovascular disease by 30%. Researchers emphasize that primary care providers can integrate the new intervention as a sustainable, cost-efficient strategy to prevent type 2 diabetes on a large scale.

For more information, including on the institutions participating and collaborating with the project, see the press release of the University of Navarra.

Reference

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. August 26, 2025. doi:10.7326/ANNALS-25-00388

Linked editorial

Franz MJ, Daly A. Modest Weight Loss With a Mediterranean Diet and Physical Activity: A Feasible Strategy to Prevent Type 2 Diabetes? Ann Intern Med. 2025. https://doi.org/10.7326/M25-2175