This article deals with Eating Disorders (ED) and is aimed at discovering if is there any significant sex difference in ED in teenage students, evaluating attitudes and behaviours related to anorexia and bulimia nervosa, exploring the personality traits of ED students and analysing the obsession with thinness as an essential characteristic of these kind of problems. The investigation, conducted in Granada from 2007 to 2010, used an eclectic approach based on collecting quantitative and qualitative data. In this article only quantitative data is presented. Regarding the sample, we worked with secondary education pupils in the three "Juan XXIII" High Schools in Granada. The selection of the sample is based on age criterion, in this case from 11 to 17 years-old people, a defining moment in life because when important decisions for their personal and professional future at the end of compulsory education are made. Results point to educational and guidance needs in people with ED, and differences between men and women. In addition to this, these students show deficiencies in some areas, which expose them to suffering any eating disorder, especially around 13 years of age, when they are weakest and prone to be involved in this kind of disorders.