Socio-economic metabolism (SEM) occupies a central place in the study of agri-food systems. While researchers are asked to address growing environmental and social issues, the link between theoretical choices of representation and action is rarely discussed as such. We propose a cross-sectional analysis between the way SEM is described and how researchers propose to act, based on a literature concerned with agri-food systems. We distinguish the metabolism representations based on funds, flows and stocks, scales and levels, as well as socio-economic analysis. Action is seen through the operational goals pursued by the researchers, the action-research interfaces in which they engage, and the partners with whom they interact. We identified eight schools of thought related to three different types of representations: (1) space and compartment-based representations; (2) economic agent-based representations; and (3) multi-faceted and composite representations. We show that metabolism representations and action are deeply intertwined. The analysis of the biophysical basis of society is neither independent of normative claims regarding how this basis should evolve, nor of the means to get there. We then discuss the consequences of this fact on the choices of representation of metabolism and particularly the interest of anchoring SEM in pragmatism.