Girls-only vs. mixed-gender groups in the delivery of a universal wellness programme among adolescents: A cluster-randomized controlled trial

BACKGROUND: Investigation of the optimal setting for body image prevention programmes is important to maximize the outcomes of such programmes. OBJECTIVES: We examined the preferred setting for a school-based wellness programme called “In Favour of Myself". METHODS: A total of 259 girls (mean 13.82±0.64 years) were divided into a girls-only intervention group, a mixed-gender intervention and a waiting list control group. The participants completed self-report questionnaires at baseline, post-intervention (2 months) and at follow-up (3 months) examining changes in self-esteem, media literacy, body image and risk factors for eating disorders. The intervention group participants also completed a satisfaction questionnaire. RESULTS: Both intervention groups demonstrated statistically significant improvements in identifying advertising strategies (p<0.01) compared with the controls, with the girls-only arm (p<0.001) showing better results. Compared with the girls-only arm and the control group, the mixed-gender group demonstrated statistically significantly greater improvements in the internalization of pressure for thinness (p<0.004), the body-esteem appearance subscale (p<0.025) and body-esteem body-weight subscale (p<0.012) as well as reductions in their perceived current body silhouettes and in the gap between their current and ideal body image (p<0.003). Body dissatisfaction was increased following the programme, although not in a statistically significant manner, with the worst negative effect observed in the girls-only arm. All other differences among the study arms did not show statistically significant differences. Mediation models revealed that body-esteem was directly mediated by group, with statistically significant mediation only in the mixed group. Current body image was mediated indirectly by group through media literacy (i.e., recognizing advertisement strategies and internalization of pressure for thinness), with statistical significance only in the mixed-gender arm compared with the girls-only arm. Higher programme satisfaction was reported in the mixed-gender group (91%) vs. the girls-only groups (79%). CONCLUSIONS: These outcomes provide preliminary evidence indicating the superiority of a mixed-gender setting compared with a girls-only setting for delivering prevention programmes to 13- to 14-year-old adolescents to enhance their media literacy, positive self-esteem and body image. TRIAL REGISTRATION: NCT02653586