Unhealthy dietary behaviours are a major threat to public health, in which the modern food-retail environment (e.g., supermarkets) have a substantial role. In recent years, there has been a growing realization that these environments are themselves the products of underlying systemic factors and dynamics, which obstruct attempts to address these environments. In this thesis we set out to explore this issue, with the objective “to acquire insight into the factors in food-retail systems which underlie the persistence of drivers of unhealthy dietary behaviours in retail food environments, and to explore how a transformation of these systems can be realized, in order to contribute to healthier dietary behaviours.” We explored this problem through a transition theory lens, in which we combined Multi-Level and Constellation Perspectives. Our research activities focussed on the Dutch context, in which we examined the SUPREME NUDGE project, which aimed to develop and trial health promotion interventions in collaboration with a Dutch supermarket chain, as a case study. Five separate studies were performed: 1) A systematic literature review method, which explored implementation barriers and facilitators and underlying systemic factors for health interventions in food-retail settings. 2) A system analysis, which combined historical literature, with semi-structured interviews on the Dutch food-retail system, to explore the dynamics and factors which promote unhealthy food-retail environments. 3) A co-creative design process in which supermarket actors took part in the development of a multi-component intervention to promote healthier diets in supermarkets. 4) A reflexive monitoring study, in which the implementation of the previously developed intervention was monitored, and used to reflect upon, and seek underlying causes of and solutions for, observed implementation issues. 5) A roadmapping study, in which representatives of relevant stakeholders for the Dutch food-retail system collaborated to decides what steps would ...