Research has put effort in characterizing the socio-economic metabolism of cities with respect to food. Most of these studies use a material or substance balance approach considering a city’s food system as a black box. However, the way food circulates within a city is of major importance in the perspective of sustainability and socio-ecological transition. This is the purpose of this proposition that aims at enriching urban metabolism studies through the analysis of the food system. We use a hybrid food system – urban metabolism approach to characterize food flows within a city’s boundaries, and use Paris and its region as a case study. We estimate the “eating population” by calculating the “eating resident equivalent” for different resident and non-resident populations, adapted from the “population equivalent” concept rooted in the organic wastewater pollution literature. We analyze statistics about food purchase, food intake and food-related practices of the Paris region residents to calculate the amount of food circulating between different food system sectors. Our analysis enables us to seize the magnitude of wasted food. We expect to present the calculation results. The novelty of our approach lies in a detailed analysis of the urban metabolism within urban boundaries. Although a large share of the environmental footprint of urban food systems is embodied within imported food, cities are increasingly willing to politically intervene within their scope. Characterizing the circulation of food for a city’s eating population is an important step towards policy intervention.