Mediterranean Diet Plus Lifestyle Changes Prevent Type 2 Diabetes

Prof. Nelly Pitteloud August 26, 2025

A powerful new study confirms that modest but consistent changes in diet and lifestyle can dramatically reduce the risk of type 2 diabetes.

Researchers found that combining a lower-calorie Mediterranean diet, daily exercise, and ongoing nutritional support reduced diabetes risk by 31% among overweight and obese adults aged 55 to 75.

These results come from the PREDIMED-Plus trial, the largest European nutrition study to date, involving more than 6,800 participants across 23 research centers in Spain. The findings were published in the Annals of Internal Medicine.

Notably, the role of diet, exercise and weight loss in reducing diabetes risk was established in a landmark trial from the Diabetes Prevention Program (DPP) published in the NEJM in 2002. Patients who were randomly assigned to receive education, exercise at least 150 minutes a week and follow a low-calorie, low-fat diet to reduce their weight by 7 percent saw a 58 percent reduction in their risk of diabetes compared with the placebo group.

The Key Findings

• 31% lower risk of type 2 diabetes over 6 years.

• Weight loss: About 3–4% of body weight on average.

• Waist reduction: Significant decrease in abdominal (visceral) fat.

• Better body composition: Less fat mass, more preserved muscle.

• Sustained adherence: Participants maintained changes for 6 years — a rare success in long-term lifestyle trials.

  
  

The study shows that modest, sustained changes in diet and lifestyle could prevent millions of cases of type 2 diabetes worldwide.

Study design

All 6,874 participants, either overweight or obese, age 55 to 75, participated in the study. While no one was diagnosed with type 2 diabetes at the start of the study, all participants had metabolic syndrome, defined as high blood pressure, high blood sugar, altered cholesterol and excess fat around the waist, that increase one's risk of developing diabetes and other chronic disorders.

The participants were randomly assigned either to an intervention group or to the control group.

• Those in the intervention group met with a dietitian regularly for six years and were counseled on how to follow the Mediterranean diet and were also counselled how to reduce calories — about 600 calories a day. They were also advised on adopting an exercise program of 45 minutes per day, six days a weekl.

• Those in the control group received only education on the Mediterranean diet, and they met with dietitians less frequently.

• All participants received one liter of olive oilmonthly for free, an expensive component of the diet.

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What is the Mediterranean diet?

Studies have found the Mediterranean diet can reduce the risk for diabetes, high cholesterol, memory loss, depression, and breast cancer.  

• Base: Vegetables, fruits, legumes, nuts, whole grains

• Healthy fats: Olive oil as the main fat source.

• Protein: Fish, small portions of poultry, occasional dairy, eggs.

• Red meat: Rarely, usually as a flavoring.

• Sweets & refined foods: Reserved for special occasions.

• Lifestyle: Eating socially, savoring meals, staying active daily.

Thirty-one percent lower risk of type 2 diabetes over 6 years

 At first glance, the results might seem obvious — eat better, exercise, lose weight, prevent diabetes. What is staggering is the 6-year adherence with very little recidivism emphasizing the long-term adherence. These participants made LASTING lifestyle changes, what makes this trial exceptional.

The benefits went beyond the 31% lower risk of type 2 diabetes:

• Decrease weight by 3-4%

• Reduction in visceral adiposity (belly fat), which drives insulin resistance.

• Improved body mass index (BMI) and metabolic markers.

• Preservation of lean muscle mass thanks to exercise.

  
  

It’s not just weight loss, but also improvement in body composition that may have contributed to the reduction in diabetes risk.

What Made the Difference?

Participants in the intervention group:

• Followed a Mediterranean diet with ~600 fewer calories per day.

• Limited added sugars, refined carbs, processed meats, and sugary drinks.

• Ate plenty of extra-virgin olive oil (supplied free: 1 liter/month) and fish

• Ate plenty of vegetables, fruits, legumes, nuts, whole grains rich in fibers.

• Exercised 45 minutes/day, 6 days per week, including strength and balance training.

• Received intensive behavioral support:

  • Dietitian visits 3× per month in year 1.

  • Monthly group sessions + quarterly individual follow-ups for 5 years.

    
    

The control group also received free olive oil but only general advice twice a year — no calorie restriction, exercise program, or structured weight loss plan.

Why It Matters Globally

• 530 million people worldwide live with type 2 diabetes.

• In Spain, 4.7 million adults are affected.

  
  

Metabolic syndrome — defined by high blood sugar, high blood pressure, abnormal cholesterol, and central obesity — remains one of the strongest predictors of diabetes and cardiovascular disease.

This trial shows that prevention is both possible and practical.

What is the key factor in this study?

We know that long before Type 2 diabetes or prediabetes presents, patients commonly develop insulin resistance, a condition in which their body doesn’t respond as well to insulin. Physical activity and high-fiber diets like the Mediterranean diet — as well as weight loss — can help reduce that resistance.

The diet, exercise and weight loss could also reduce inflammation and oxidative stress, a process that damages cells, researchers said. Together, the benefits may lower diabetes risk.

Participants in the treatment group had regular and frequent contact with a dietitian, whereas the control group didn’t receive the same level of guidance. It’s unclear how much of a factor this support was, versus the dietary and activity intervention itself.

Takeaway

• Even modest weight loss (3–4%) reduces diabetes risk.

• Daily movement — especially walking plus resistance training — preserves muscle and reduces belly fat.

• Professional guidance helps maintain adherence long-term.

• The Mediterranean diet is flexible, enjoyable, and sustainable.

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