Integrating Mediterranean Diet Education and Sustainability in Primary Schools: A Two-Season Community-Based Intervention in Portugal.

Background/Objectives: School-based programmes may play an important role in promoting healthier and more sustainable dietary habits from early childhood. This study described and evaluated a community-based intervention aimed at promoting Mediterranean diet (MD) principles, improving food literacy, and raising awareness of sustainable food practices among primary school children in the Tagus Lezíria region, Portugal. Methods: The intervention was implemented in 23 schools across 11 municipalities and included two seasonal rounds of participatory educational activities focused on healthy eating, local and seasonal foods, sensory exploration, balanced meals, composting, food storage, sustainable food production, and food waste prevention. A total of 872 children participated in the intervention activities, and 370 provided paired baseline and follow-up KIDMED assessments. Results: The mean KIDMED score decreased significantly from 8.0 ± 2.2 at baseline to 7.5 ± 2.4 after the intervention. Overall, 31.6% of participants improved their score, 18.9% showed no change, and 49.5% showed a decrease. The proportion of children who did not skip breakfast increased from 79.8% to 88.6%, and avoidance of fast-food restaurants more than once weekly increased from 85.4% to 89.6%. Smaller favourable changes were observed for pastry, sweet, and fish consumption, and olive oil use, whereas fruit, vegetable, pulse, and nut consumption did not improve. Conclusions: The intervention produced heterogeneous outcomes. Although overall MD adherence decreased, almost one-third of participants improved individually, with favourable changes in breakfast and selection of less healthy behaviours. Longer programmes with stronger family involvement may be required to reinforce core MD foods and achieve broader, sustained improvements.