A new study has found that combining a Mediterranean-style diet with calorie control, regular physical activity, and professional weight loss support can lower the risk of developing type 2 diabetes by 31%.
The study, co-authored by researchers from the Harvard T.H. Chan School of Public Health, was published on August 25, 2025, in the Annals of Internal Medicine.
The Mediterranean diet focuses on eating mostly fruits, vegetables, whole grains, and healthy fats such as olive oil. It also includes moderate amounts of lean protein and dairy, while limiting red meat and processed foods. This diet has been linked to better heart and metabolic health in many past studies.
In this new research, scientists wanted to find out whether adding more lifestyle changes to the Mediterranean diet could make it even more effective at preventing type 2 diabetes (T2D), a serious condition that is becoming more common worldwide.
Millions of people around the globe are developing diabetes, said Frank Hu, a senior author of the study. He is a professor at Harvard and chair of the Department of Nutrition. He added, Our results show that small but lasting changes in diet and lifestyle could prevent millions of diabetes cases.
The study used data from the PREDIMED-Plus clinical trial, the largest nutrition and lifestyle trial in Europe. Researchers from 23 universities in Spain and Harvard followed 4,746 people for six years.
All participants were between the ages of 55 and 75, overweight or obese, and had metabolic syndrome—a group of risk factors linked to heart disease and diabetes. None of them had type 2 diabetes when the study began.
Participants were split into two groups. One group followed a traditional Mediterranean diet with no added guidance or support.
The other group also followed the Mediterranean diet but with key additions: they reduced their calorie intake by about 600 calories a day, added moderate physical activity such as walking and light strength exercises, and received help from professionals to support their weight loss goals.
After six years, the results were clear. The group with the full lifestyle intervention was 31% less likely to develop type 2 diabetes compared to the group who only followed the diet.
On average, the intervention group lost 3.3 kilograms (about 7.3 pounds) and trimmed 3.6 centimeters from their waistlines. In contrast, the control group lost just 0.6 kilograms and 0.3 centimeters from their waists.
In everyday terms, these changes meant that around three out of every 100 people avoided developing diabetes, said Miguel Martínez-González, a professor at the University of Navarra and Harvard Chan School. That’s a real win for public health.
This study gives strong evidence that while the Mediterranean diet is healthy on its own, combining it with modest calorie reduction, regular exercise, and ongoing support makes it even more powerful in reducing diabetes risk. It also shows that sustainable, manageable changes to one’s routine can make a big difference in long-term health.
As diabetes continues to affect more people around the world, this study highlights a simple and effective strategy to help prevent the disease—one meal, one walk, and one healthy habit at a time.
If you care about diabetes, please read studies about New diabetes drug could control blood sugar and body weight better and findings of Common diabetes drugs linked to increased heart risk.
For more about diabetes, please read studies about Why diabetes drug metformin can help increase longevity and findings of This drug could manage type 2 diabetes for a long time.
The study is published in Annals of Internal Medicine.
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