A study protocol for a preliminary randomised controlled trial assessing the acceptability and effectiveness of two eating disorders prevention interventions in Switzerland: The HEIDI BP-HW project.

Because of the serious consequences of eating disorders on young women's lives and because of the lack of specialised care facilities, assessing and implementing evidence-based prevention interventions is necessary. Switzerland, like other Western countries, has high prevalence rates of eating disorders. However, no prevention interventions have been evaluated in this country so far. This paper presents the protocol of a preliminary study with the aim to evaluate the acceptability and effectiveness of two interventions, the Body Project (BP) and the Healthy Weight Program (HW), for female students from French-speaking Switzerland. These two interventions were chosen because they have been widely evaluated and they proved to be effective in various countries. They take place in groups and include four weekly sessions over one month. Because of the pandemic situation, the group sessions will take place online on an collaborative platform. The design is a three-arm randomised controlled study. Ninety female students aged 18-25 and presenting with at least moderate body dissatisfaction will be randomised into three groups: (1) one-month BP intervention, (2) one-month HW intervention, and (3) one-month waiting-list control group followed by the BP intervention. Assessments of body dissatisfaction, thin-ideal internalisation, dietary restraint, negative affect, and eating disorder psychopathology will be conducted before and after the interventions or waiting list and after a one-month follow-up. ANCOVA and ANOVA with repeated measures will be used to assess group differences and follow-up stability. Acceptability will be assessed with a questionnaire on participants' satisfaction with the interventions, group discussion at the end of the intervention, and with participants' rate of attendance to the group sessions. The study results will provide additional data on these two eating disorders prevention interventions and will suggest ways for their dissemination and further evaluation in Switzerland.