In a context of growing attention to the issue of feeding the city, this article focuses on the role of the assessments guiding the processes of urban food policy and planning to reach Sustainable Food Security. The starting point is a collection of experiences dealing with some cities that in recent years have launched strategies for developing healthier and more sustainable food systems. Their analysis highlights the innovations in the construction of cognitive frameworks supporting food policies and planning, as well as the difficulties to explore the food phenomenon on the qualitative and quantitative level. Within a current research meant to address the food agenda in Venice, the authors take advantage from the case studies comparison to propose key themes and investigation methods a preliminary assessment of the existing food system. Considering the strong impact of the huge tourist flow that invests the city, daily, the foodservice sector is considered as the main challenging and strategical core-area for boosting impactful changes in the urban food system.