The concept of system food of the medium (SyAM) was born from the assumption of a hybridization combining the best of the short and the long food circuits. The SyAM Project has explored the forms of the hybridization, and carried out a close analysis of the SyAM components, so that to conceptualize it. But, during these works we have been surprised by how the economic, environmental and social values shared inside a SyAM was also shared by the team members (researchers and fields actors), and even more promoted by the mean of the SyAM concept. Thus, we studied this voluntarist dynamic and its influence on the construction of this concept, through an abductive and reflexive approach. Its epistemic nature was analyzed. This paper has two goals: to present this concept and its construction; to propose the notion of activist concept to describe its epistemic nature and help a reflexive and ethic analysis. The first part studies the SyAM concept as an object. The second discusses its projective dimension. Then, the last part questions it through the grids of five concepts (boundary object, umbrella concept, transitory representation, thick ethical concepts and integrative object), proposes the notion of activist concept, and suggests some uses. Indeed, it is an invitation to an ethical reflexion that urges to question the implicit and the obviousness within our choices, and the values within the distrusts and confidences that lead our researches. Think about the potential activism level of ours concepts would improve the conception of the research works and their results. Considering what the activist concept enlightens could contribute to the evaluation of the research projects and their results.