Based on a corpus of fifty semi-structured interviews conducted among the working-class, this paper presents an analysis of perceptions and appropriations of “Diet / Physical Activity” self-quantification tools in low-income milieus. It shows limited use of self-tracking tools and, based on an examination of a “digital divide,” highlights the factors leading to reluctance or adherence regarding the use of new self-quantification technologies. These technologies involve a relationship with food and time that is at odds with the taste for freedom found in working class milieus. The desire to escape from daily constraints causes respondents to steer clear of self-measurement approaches. Analysing the tension between the fears linked to tracking devices and hopes of empowerment, this article concludes with a description of those segments of the working class to which self-tracking tools are a means of emancipation.