The objective of this paper was to determine the efficacy of a program applied to 115 girls in 1st and 2nd grade in Secondary Obligatory Education (ESO) (average age=12.71; SD=0.72) in six sessions to prevent the onset of eating disorders. Pre-, post-program and after a one-year follow-up, the EAT-40 and BSQ were applied. Additionally, a questionnaire was created to assess the capability of identifying risk factors in ED development. The results were contrasted with those obtained from a group of girls (N= 69) in the same grades and of the same age (average age=14.36; SD=0.54) who did not participate in the prevention program (PP). Participants were already showing very low scores on both questionnaires from the pre-program. The effects of the intervention were scarce, although it was observed that a high capability of identifying risk factors had been acquired. When compared to the non-participants and after the one-year follow up, the participants showed significant lower eating and body image pathologies. The program has proven its efficacy both in short and long-term and the ideal school year to apply it is 2nd grade ESO.