The growing appetite of cities is one of the greatest future challenges. There is no set menu for meeting this appetite, but a trend is observed in which city authorities focus on region-based food provision. Regionalism is motivated by the importance of increased self-reliance. Besides, regional food systems, are associated with more sustainable production and reduced carbon footprints, the reconnection of consumers with production, and the increased uptake of whole foods in urban diets. However, the question remains to what extend region based food systems may become self-reliant? How may they contribute to improved sustainability and healthy lifestyles? With the Dutch city of Almere as a case in point this paper provides a food flow data-based analysis of the opportunities and limitations of regional based food system approaches. The paper sets off with defining the concepts of sustainable self-reliance and regionalism. Next, it describes the methodology of measuring and mapping the actual food flows. We combined secondary, publicly available, with primary quantitative and qualitative datasets, involving regional businesses, urban policymakers, and residents. Our study uncovers the coinciding disconnect and interconnectedness of local, regional and global food systems. The regional scale offers opportunities for tackling many food related challenges, however, sustainable urban food security demands connections beyond the regional sphere and beyond the food domain. To assess the effects of the policy options available at the local and regional level, a solid evidence base is essential. This paper advances the development of evidence-based methodologies to monitor and inform food system policies.