Transitioning to diets with less animal-based and more plant-based food is crucial for addressing environmental and health concerns. Although nutrition behaviour has been extensively studied in the literature, fewer studies have been carried out on the determinants of meat consumption. To fill this gap, the NO-MORE-MEAT project aims to study both the psychological and structural factors influencing meat consumption to develop effective behaviour change interventions. The project is organised as follows: 1. Observational Studies (WP1): Online surveys and semi-directive interviews will identify psychological and structural factors related to meat consumption. Participants will be recruited from an open web cohort (NutriNet-Santé study), including students from disadvantaged neighbourhoods and through a panel company. 2. Interventional Studies (WP2): Laboratory-based behaviour change interventions will be developed and tested to assess their impact on psychological factors and meat consumption. Participants will be recruited through a panel company. 3. Protocol Development (WP3): A theory- and evidence-based behaviour change intervention targeting meat consumption reduction and its evaluation (a longitudinal follow-up) will be developed based on WP1 and WP2 results ad will be developed through participatory research. Open Science and Risk Management: The proposal follows open science principles, with materials and data being made available. Moreover, concerns about recruitment bias and ethical issues are addressed, with plans to ensure diverse participant recruitment and ethical approval. Relevance to Research Theme: The research project aligns with the theme of “Santé publique, santé et sociétés” by exploring factors and determinants of health, including the impact of meat consumption on health and sustainability. The project aims to contribute to public policy strategies on promoting healthy and sustainable eating.