This dissertation falls within a tradition that investigates the making of health-related problems into social problems. Using literature reviews, document analysis, and qualitative and quantitative coding of medical publications from 1950 to 2010, I argue that both our increasingly individualistic culture and our collective faith in science fuel the current fear of obesity and lead to the expansion of the medical discourse on fat. In Part I, I review the main medical research paradigm on obesity, which argues that fat is bad for your health, before turning to the critique of this paradigm, and show how both sides of the debate use science to justify their stance. I then combine both views to identify which educational strategies are most likely to be implemented, and efficient. The importance of stigma in the health and well-being of obese people appears to be critical to this effort. Part II contributes a timeline for distinct but overlapping conceptualizations of bodily fat in the medical literature, and shows the massive and recent increase in medical interest in obesity. From merely an individual trait, fatness has become a medical problem (obesity), a social problem and an epidemic, and has culminated in recent years into a focus on children: the so-called epidemic of childhood obesity. This longitudinal approach to the medical literature at both the aggregate level (in the PubMed database) and in the most cited articles on obesity highlights the historical contingency of our cultural and medical obsession with fat, meanwhile identifying the role schools are expected to play.