Effectiveness and cost-effectiveness of an online school-based programme to reduce eating disorder risk factors in preadolescents (PRETA): protocol for a cluster-randomised controlled trial.

introductionEating disorders are complex mental health conditions characterised by pathological behaviours related to food intake, often accompanied by a chronic obsession with weight control. Their prevalence is increasing, with an earlier onset and greater severity among young people. Universal prevention, through multicomponent strategies that tackle modifiable risk factors, has emerged as a promising tool. This paper reports the study protocol designed to assess the effectiveness and cost-effectiveness of the PRETA (Prevención de los Trastornos de la Alimentación) programme in reducing the risk of eating disorders and related modifiable risk factors among preadolescents in the school setting. METHODS AND ANALYSIS: The PRETA programme will be assessed by means of an open, community-based, multicentre, controlled trial using 1:1 matched-pairs cluster randomisation at the school level. Schools in Tenerife (Spain) will be assigned to the PRETA programme or a waitlist control group. Participants include 5th- or 6th-grade students (10-13 years old), their parents and teachers. The PRETA programme is a universal, school-based, multicomponent programme designed to reduce eating-disorder risk and modifiable risk factors. Its main component is an interactive online platform called e-PRETA, complemented by training sessions for families and teachers. e-PRETA includes nine 45-minute sessions addressing risk factors, such as dietary habits, beauty standards, media literacy, self-esteem, emotional regulation and social skills. A total of 1068 children from 12 schools will participate. The primary outcome will be the risk of developing eating disorders (Children's Eating Attitudes Test-26 item version). Secondary outcome measures are body dissatisfaction (Adapted Contour Drawing Rating Scale), eating disorder traits (Eating Disorder Inventory-2), internalisation of appearance ideals (Sociocultural Attitudes Towards Appearance Questionnaire-4) and self-esteem (Rosenberg Self-Esteem Scale). Outcomes will be assessed at baseline and postintervention (3 months). Additional baseline covariates such as electronic device use, parental feeding attitudes, physical activity, sleep duration and screen time will also be collected. Programme effectiveness will be analysed using generalised mixed models. Cost-effectiveness will be assessed by comparing the incremental costs associated with the implementation of the PRETA programme with its estimated effectiveness. ETHICS AND DISSEMINATION: Ethics approval has been obtained from the Ethics Committee for Research with Medicines at the University Hospital of the Canary Islands (CHUC_2021_78). Written informed consent will be obtained from the parents or legal guardians of all participants. Results will be disseminated through scientific publications and conferences. TRIAL REGISTRATION NUMBER: NCT06792981.