Interventions and assessments
thinness, cognitive dissonance
The participants were informed of the intervention they were receiving. Participants completed online questionnaires at three time points: (1) before the start of the intervention or the waiting period, (2) four weeks later at the end of the intervention or waiting period, and (3) one month later.The participants in the BP group received the intervention in four weekly sessions of 90 min, scheduled at the end of the day after school. Two facilitators, the first author, who is a psychologist and an assistant who is a dietitian of a similar age to the participants, led the groups via Teams®, a virtual platform widely used for teaching activities during the 2020 lockdown. We used a French translation of the BP script. The team was trained by the translator of the manual, a researcher at the University of Grenoble-Alpes (France). During the four weeks of intervention, participants were encouraged with discussions and exercises to behave and speak against the current beauty ideals, such as thinness and muscularity, to create cognitive dissonance and distance them from their ideals.The participants in the HW also received the intervention in four weekly sessions of 90 min, scheduled at the end of the day after school. Two facilitators, the third author, who is a dietitian and an assistant, also a dietitian, with a similar age to the participants, led the groups via Teams®. We translated the script following the original framework, which includes psychoeducation behavioral change techniques, to encourage participants to implement small changes in their lifestyle for health and well-being, as well as group discussions on the encountered difficulties. However, the advice given as a source of inspiration to choose which changes to implement to aim for a health ideal instead of a thin ideal was adapted to the Swiss recommendations for a balanced diet and physical activity. These recommendations included four parts: what, how much, when and how. The advice was given on the quality (what) and quantity (how much) of food and physical activity that had to be aimed for. “When” included advice regarding the structure of the day, and “how” recommended relying on internal cues and feelings to reconnect with food intake and physical activity that would be satisfying and positive for health, without focusing on weight.The participants in the WLCG had to complete two assessments, each separated by a one-month interval, during which they received no intervention. They then received the BP, because that intervention showed the largest effects [