A traditional Mediterranean diet already helps prevent type 2 diabetes. The open question for the last decade has been whether adding a calorie cut and structured exercise on top would push that benefit further. The PREDIMED-Plus trial, published in Annals of Internal Medicine in 2025, ran the experiment in 4,746 Spanish adults followed for 6 years. The answer is yes, by a further 31 percent.
The trial enrolled adults aged 55 to 75 who were overweight or obese, had metabolic syndrome, and had no prior diabetes or heart disease. One arm followed an energy-reduced Mediterranean diet with a 600 kcal daily deficit, a structured physical activity programme, and behavioural coaching. The other arm received standard Mediterranean diet advice without calorie targets or exercise prescription. Cumulative incidence of new diabetes was 9.5 percent in the intensified arm versus 12 percent in the control arm. The curves separated within the first 6 months and widened through to year 6.
What the trial measured
PREDIMED-Plus is a parallel-group, randomised, single-blind trial run across 23 Spanish centres. Participants in the intensified arm followed three coordinated changes. First, an energy-reduced Mediterranean diet calibrated to a 600 kcal daily deficit from estimated needs, built around vegetables, legumes, whole grains, fish, nuts, and extra-virgin olive oil, with red meat, sugar-sweetened drinks, and refined grains kept low. Second, a stepwise physical activity programme that started at 45 minutes of brisk walking 6 days a week and added strength, flexibility, and balance exercises. Third, behavioural support every 1 to 3 months from trained dietitians, with personalised goal-setting around weight, food, and activity.
The control arm received traditional Mediterranean diet education with no calorie target, no exercise prescription, and lighter contact every 6 months. Both groups received quality extra-virgin olive oil and nuts to remove cost as a barrier.
The primary outcome was incident type 2 diabetes confirmed by fasting glucose, HbA1c, or 2-hour glucose tolerance test, adjudicated by an endpoint committee blinded to assignment. Median follow-up ran 6 years.
What the results showed
The intensified arm had 31 percent fewer new diabetes cases relative to control. In absolute numbers: 9.5 percent of the intensified arm developed diabetes versus 12 percent of the control arm. The Kaplan-Meier curves separated within the first 6 months and continued to diverge through 6 years, a pattern consistent with a sustained biological effect rather than chance variation.
The result builds on PREDIMED-Reus, an earlier trial published in Diabetes Care in 2011. That study randomised 418 high-risk adults to a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with nuts, or a low-fat control. After a median 4 years of follow-up, the two Mediterranean arms cut diabetes incidence by roughly half versus low-fat advice alone, without calorie restriction.
Read the two trials together and a clear pattern emerges. Switching from a Western or low-fat diet to a Mediterranean pattern delivers most of the diabetes-prevention benefit. Layering on a moderate calorie deficit and structured exercise adds another 31 percent on top. The added cost is more contact with a clinician or coach, not a more restrictive plate.
The protocol in plain English
The intervention is reproducible without a Spanish clinic. Five steps cover the substance.
Why this works for UK adults
Type 2 diabetes is one of the largest preventable disease burdens in the UK. NHS guidance is clear that body composition, diet quality, and physical activity are the primary modifiable risk factors. Most cases of type 2 diabetes in adults with metabolic syndrome or pre-diabetes are preventable with the kind of intervention PREDIMED-Plus tested.
The NHS Diabetes Prevention Programme already runs a similar model in England. A 2022 evaluation in The Lancet Regional Health Europe found a measurable population-level reduction in type 2 diabetes incidence linked to programme rollout. PREDIMED-Plus reinforces the case that the strongest protection comes from layering food quality, modest energy restriction, and consistent moderate exercise rather than relying on any single change in isolation.
Common mistakes to avoid
Cutting calories without enough protein loses muscle alongside fat. Aim for 1.2 to 1.6 grams of protein per kilo of bodyweight daily, spread across meals during a calorie deficit. Replacing breakfast bread with the same bread plus a sugary cereal does not bring a Mediterranean pattern, regardless of the olive oil at dinner. The 600 kcal cut works only if the calorie cap is real, not nominal. A 45-minute walk delivers metabolic benefit when it raises breathing and warms the body, not when it is a slow amble. If the heart rate stays close to resting level, the dose is missing.
Frequently asked questions
Bottom line
A Mediterranean diet pattern alone protects against type 2 diabetes. Adding a 600 kcal daily deficit and a structured walking-plus-strength programme on top cuts the relative risk by a further 31 percent over 6 years, per the 4,746-participant PREDIMED-Plus trial. The intervention is replicable at home with no special equipment. The change starts in the kitchen and on the pavement, not at the pharmacy.
Sources
- PREDIMED-Plus Investigators. 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. Annals of Internal Medicine, 2025, vol 178, no 10. acpjournals.org/doi/10.7326/ANNALS-25-00388
- Salas-Salvado J, Bullo M, Babio N, Martinez-Gonzalez MA, et al. Reduction in the Incidence of Type 2 Diabetes With the Mediterranean Diet: Results of the PREDIMED-Reus nutrition intervention randomized trial. Diabetes Care, 2011, vol 34, no 1, pages 14 to 19. PMID 20929998. pubmed.ncbi.nlm.nih.gov/20929998
- Authors et al. Population level impact of the NHS Diabetes Prevention Programme on incidence of type 2 diabetes in England: An observational study. The Lancet Regional Health Europe, 2022. PMID 35664052. pubmed.ncbi.nlm.nih.gov/35664052
- NHS. Type 2 diabetes. nhs.uk/conditions/type-2-diabetes
- WHO. Healthy diet. who.int/news-room/fact-sheets/detail/healthy-diet