Funding for this research was provided by:
Received: 14 May 2019
Accepted: 10 January 2020
First Online: 22 January 2020
Ethics approval and consent to participate
: There is no formal institution for ethical assessment and approval of questionnaire-based population studies in Denmark. The Regional Scientific Ethical Committee, the Capital Region of Denmark, reviewed the HHS study and concluded that formal ethical approval was not required, ref.: 16018722. The HHS study is registered at the Danish Data Protection Agency, ref.: 2015-57-0008. When high schools were invited to participate, written information was sent to principals, teachers and student councils at all high schools explaining the implications of participating in the study. For all data collection methods, respondents were informed about the aim of the study, that participation was voluntary, that their information would be used for research purpose only and treated with confidence. In the written introduction to the questionnaires, respondents were asked to click the button ‘next’ at the bottom of the page if they accepted to participate in the questionnaire data collection (passive written consent). Moreover, they could skip questions they did not want to answer. All participants provided verbal, voluntary and informed consent before participating in the qualitative data collections. According to the Danish Data Protection Agency, the given consent may be written or verbal [CitationRef removed]. The needs assessment confirmed that mental health issues, body image and eating behaviours are sensitive issues among adolescents. We payed special attention to this in the design of intervention materials, interview guides and questionnaires. The main message of the intervention program communicated to students was ‘to boost your energy during the school day’. We applied the term movement instead of PA in the intervention material and other project communication to the schools and students to reflect that we encouraged all types of movement. Finally, we did not focus on counting calories but on eating regular meals to maintain energy levels throughout the school day.
: Not applicable.
: The authors declare that they have no competing interests. The HHS app and website were developed by Mobile Fitness International ApS. Mobile Fitness International ApS was not involved in the study design, data analysis or interpretation of data.