Reduced-Calorie Mediterranean Diet Protects Against Diabetes
The Mediterranean diet, which includes fresh fruits and vegetables, whole grains, nuts, legumes, fish, olive oil, reduced calorie intake and moderate physical activity, can reduce the risk of type 2 diabetes by 31%, according to a new study, “Comparison of an Energy-Reduced Mediterranean Diet and Physical Activity Versus an Ad Libitum Mediterranean Diet in the Prevention of Type 2 Diabetes.”
The International Diabetes Federation predicts that over 850 million people worldwide will be living with diabetes by 2050. In Europe alone, more than 61 million people now live with type 2 diabetes– about one in 10 people. In 2021, treating type 2 diabetes in Europe cost more than 160 billion euros. This challenge is compounded by a shortage of health workers, and during the pandemic, people with diabetes were particularly vulnerable. Research like this highlights the power of lifestyle changes we can make ourselves.
A Mediterranean diet combined with reduced calorie intake and moderate physical activity can lower the risk of developing type 2 diabetes by 31%, compared with following a standard Mediterranean diet without calorie restriction.
This is the main finding of the PREDIMED-Plus study, a large Spanish multicenter clinical trial coordinated by the University Rovira i Virgili with the participation of more than 200 researchers from 22 institutions across Spain. PREDIMED-Plus is also the most important European nutrition trial.
Researchers from 23 Spanish universities and Harvard Chan School followed 4,746 PREDIMED-Plus participants divided into two groups for six years. Participants with overweight or obesity and metabolic syndrome, without a history of cardiovascular disease or diabetes, were divided into two groups. To explain, metabolic syndrome is a group of health conditions that increase the risk of heart disease, stroke, and type 2 diabetes. These include high blood pressure, high blood sugar, low levels of “good” (HDL) cholesterol… The first group adopted a Mediterranean diet with reduced calorie intake (about 600 kcal less per day), a moderate exercise plan (brisk walking, strength and balance training), and professional guidance; the other followed a traditional Mediterranean diet, with no calorie restrictions or advice on exercise. The first group lost an average of 3.3 kg and reduced their waist circumference by 3.6 cm, compared with just 0.6 kg and 0.3 cm in the second group. In practical terms, this meant preventing three new diabetes cases per 100 participants.
“Our work does not end when we publish a paper. It just begins there. Science makes an impact when the findings reach the intended audience -scientists, health care professionals (actual practitioners and those in training), the general public, and policymakers”
PhD Jordi Salas-Salvadó, the senior and corresponding author of the study, is a Distinguished Professor of Nutrition and ICREA-Acadèmia Researcher at Universitat Rovira i Virgili (URV). His research primarily focuses on the effects of the Mediterranean diet on cardiovascular risk and metabolic disease. In 2021, Dr. Salas-Salvadó was recognized as one of the most cited researchers in the world. In an interview with Unknown Focus, he responded to a few questions.
The study shows that modest, sustained changes towards adopting a healthy diet and lifestyle could prevent millions of cases of this disease worldwide. This is an excellent study and of great importance. That’s why I’m interested in how important it is for such studies to be presented to politicians at a global level, especially if we consider food prices. We have excellent studies, outstanding results, and we know what needs to be done….
Professor Salas-Salvadó: Our work does not end when we publish a paper. It just begins there. Science makes an impact when the findings reach the intended audience -scientists, health care professionals (actual practitioners and those in training), the general public, and policymakers. With respect to food and nutrition, societal impact is maximized when policymakers are informed, as they have the influence and agency to make adoption of a healthier lifestyle, such as those recommended in this trial, accessible, practical, and feasible. Therefore, to maximize our social impact, we have a few strategies lined up.
Here are a few: While we are proud of this excellent paper, we will also be using both traditional and social media to communicate the messages in “bite-sized”, actionable, and simple tailored messages to directly reach academics, scientists, and even informed citizens. Our research group also participates in “pint of science” and other such initiatives that directly reach the public in an environment that they are comfortable in. Some local council members are also part of these dialogues, which help us go bottom-up to make that influence. We also teach citizens that not all that is healthy is expensive. Nutritionists and dietitians teach people to eat healthily within their budgets. For example, eating local fruits and vegetables is just as nourishing as eating exotic varieties. We believe in starting young, so we have our researchers-in-training talking to school children to inculcate good habits early. This also develops social responsibility in our younger scientists. Finally, we aim to reach policymakers and stakeholders through sharing information with succinctly created briefs and white papers. While talking to policy providers, it is always about showing how investment in prevention results in healthcare cost savings and increased productivity over time.
As Professor Salas-Salvadó further emphasizes, although health is often considered a human right, in practice, investments are made in it only when it contributes to economic productivity. They provide ideas for tools that improve public health, write scholarly articles, and collaborate with the media to convey important messages to both the public and policymakers.
“The long-term evidence generated in a large number of individuals enrolled in this study shows that this diet is sustainable. Diets of any kind can be effective only if one can be on them for a long period of time, and we have shown that the calorie-restricted Mediterranean diet is easy to follow and maintain.”
Significant financial support
At the beginning of 2025, a study was published that, among other topics, also addressed the issue of funding. Transparency is important, as it further strengthens trust, which is why scientists state in their research how and by whom projects are financed, as can also be seen in the study. PREDIMED-Plus, with more than 200 experts from 23 Spanish universities and research centers, enriches the world of science with its research. For this work to be possible, financial support came from institutions as well as various funds. For example, the PREDIMED-Plus project received an ERC grant of approximately €2,000,000, with the Carlos III Health Institute being the largest donor (€15,000,000). Additional financial support came from the Biomedical Research Networking Centre (CIBER), as well as from European funds, the Andalusian Health Agency, the Valencian Community, the United States (through two NIH projects), Canada, and other foundations and agencies.
What is the greatest advantage of this study, and what kind of change would you like this study to bring about?
Professor Salas-Salvadó: The greatest strength of this study is that it includes nearly 7000 people and follows them up for over 6 years. This kind of evidence is rare in nutrition. Usually, studies last for a few weeks or months or up to a year, at the maximum. While these studies are useful to understand mechanisms and test hypotheses, they don’t tell us about how feasible it is for people to adhere to a diet for a long time. The long-term evidence generated in a large number of individuals enrolled in this study shows that this diet is sustainable. Diets of any kind can be effective only if one can be on them for a long period of time, and we have shown that the calorie-restricted Mediterranean diet is easy to follow and maintain.
We hope these findings initiate several changes. We hope physicians and healthcare professionals take healthy lifestyle changes seriously, and as a first line of defense, even in slightly older adults. We believe that our findings will convince the general public to see that we don’t need costly gym memberships or fancy diets that taste horrible to lose weight and reduce disease risk. We have to understand aspects of what makes a healthy diet and how much of it to eat. Given that 7000 people have done it, so can everyone.
Professor Salas-Salvadó, acknowledging that his point might be somewhat controversial, asks: “Could we think about covering lifestyle counselling under medical insurance? We have shown how effective it is, so why not go this route so more people can be coached to eat healthily and exercise appropriately?”
This is supported by studies showing that lifestyle counselling, through a partnership between patients and healthcare professionals, improves the management of chronic diseases and encourages long-term changes in health behaviours. Research also confirms its additional potential to reduce healthcare system costs.
“I would do this again if I had to.”
What is your favorite part of the study, and what was the biggest challenge for you, and why?
Professor Salas-Salvadó: My favorite part of the study is, of course, seeing that we completed the study on time, with very few dropouts as planned. The study also supported the training of so many young researchers from Spain and beyond. It feels really good to have made an immediate impact through the study and also to have trained tomorrow’s leaders who will do great to define nutrition science in the future. The biggest challenge was, of course, coordinating such a large study with 23 participating centers. Coordinating funding and bringing and keeping together people since 2013. for over 10 years is not an easy feat. But we were all committed and formed a great team that always put science first.
I would do this again if I had to. COVID-19 came in so unexpectedly and caught us off guard. We couldn’t meet the participants face-to-face during the lockdown. But we quickly adapted, went online, and ensured that the participants were followed up. Like one would say, “Where there is a will, there is a way”- and we all had a very strong will!
The additional benefits
The additional benefits of the Mediterranean diet are also demonstrated in the 2021 PREDIMED-Plus study, showing that better cognitive function and adherence to the diet support weight loss, as well as improvements in memory and executive functions. However, it should be emphasized that making thoughtful and responsible choices is crucial—select foods that are nutritionally rich. In addition to maintaining a proper diet, regular medical check-ups are essential, including monitoring blood sugar levels, blood pressure, and body weight. Every small, consistent change in eating habits and lifestyle contributes to a healthier life and improved quality of life. It is important to remember that nearly 51% of the EU population aged 16 and over is overweight, and 17% is classified as obese, which further increases the risk of numerous health problems.
