After the Second world war, consumer surveys initiated by the French National Institute of Hygiene were influenced by critical positions concerning the standards and political uses of previous surveys. Notable among such critics was Jean Trémolières, director of the Institute’s nutrition section, who went against the trend of food quantification as it was developing in postwar national statistical apparatus, and also resisted the diffusion of quantified standards of conducts within the population. In this context, the data collection system developed by the INH drew both from nutritional contexts and from sociological and Catholic know-how, as seen in investigation methods and the knowledge of working-class circles. To better understand these transformations, we study the career of this young doctor. We focus on his meeting with Henri Godin during the war, which proved to be decisive and had repercussions on the very content of surveys conducted within the nutrition section he led. In particular, his participation to the “Christians of the 13th arrondissement of Paris” socialized him to survey methods as practiced by the JOC and circulated by A. Bouche and H. Desroche, collaborators in the nutrition section in the beginning of the 1950s. Nourished by investigative experiments within the JOC but also by those carried out within the Center for Sociological Studies (CES) with which the two men are associated, the nutrition section of the INH suggests ways of investigating the food which contrasts with the surveys previously developed in the field of nutrition. It introduces the notion of social environment where it had disappeared, drawing inspiration both from the methods advocated by sociologists at the CES and from the “environment” approach proposed by the Specialized Catholic Action. It is in this sense that we propose to approach the rupture introduced in the investigative practices of the INH by making the hypothesis of a “Catholic matrix”. By using this term, we are interested less in a religious belief than in a social space, where Catholics are confronted with the working-class question and more generally that of social circles.