Qualitative research which had the aim of study the knowledge and practices of school adolescents in situation of obesity. The theoretical approach was based on the theory of Paulo Freire's knowledge of education, Foucault, knowledge of reality, Le Breton the knowledge of the body and Waldow human care. It is based on the explanatory method, depth interview technique, and participant observation was used to meet the knowledge and practices made by students who have obesity and collect the data. From the interviews were conducted up to the saturation of information. The population consisted of seven students of basic level, with a diagnosis of obesity, for the analysis of the information analysis of thematic content of Minayo (2012) is worked. The results emerge two categories the first: Common Knowledge (in) the adolescent and family. The second category: The body and the teen has two at...