Background To make effective progress towards a global reduction in obesity prevalence, there needs to be a focus on broader structural factors, beyond individual-level drivers of diet and physical activity. This article describes the use of a systems framework to develop obesity prevention policies with adolescents. The aim of this research was to use the group model building (GMB) method to identify young people’s perceptions of the drivers of adolescent obesity in five European countries, as part of the EU-funded Co-Create project. Methods We used GMB with four groups of 16–18-year-old in schools in each of the five European countries (The Netherlands, Norway, Poland, Portugal and the UK) to create causal loop diagrams (CLDs) representing their perceptions of the drivers of adolescent obesity. The maps were then merged into one, using a new protocol. Results Two hundred and fifty-seven participants, aged 16–18 years, engaged in 20 separate system mapping groups, each of which generated 1 CLD. The findings were largely congruent between the countries. Three feedback loops in the merged diagram particularly stand out: commercial drivers of unhealthy diets; mental health and unhealthy diets; social media use, body image and motivation to exercise. Conclusions GMB provides a novel way of eliciting from young people the system-based drivers of obesity that are relevant to them. Mental health issues, social media use and commercial practices were considered by the young people to be key drivers of adolescent obesity, subjects that have thus far had little or no coverage in research and policy.

Engaging adolescents in obesity prevention is a main objective of the CO-CREATE project. This paper presents the development of a questionnaire to assess readiness for action and attitudes toward obesity prevention among adolescents. The questionnaire was developed based on literature searches and internal discussions with experts in the CO-CREATE consortium. The questionnaire was translated, back translated, and pretested for time and comprehensiveness by adolescents from five countries (the Netherlands, Norway, Poland, Portugal, and the United Kingdom).Exploratory factor analysis was performed, and internal reliability of the resulting factors was determined using baseline data from Poland and Norway. Furthermore, test-retest reliability was assessed in a sample of Norwegian adolescents. The exploratory factor analysis on readiness for action identified four factors. Analysis on attitudes toward obesity prevention identified four factors on responsibility and five factors on drivers of behavior. Six of the factors had a Cronbach's alpha value above 0.70, five factors had a value between 0.60-0.70, whereas the remaining two factors were below 0.60. The test-retest correlation ranged from 0.46 to 0.87. The exploratory factor analyzes on readiness for action identified the same factors as hypothesized in the development of the questionnaire, whereas attitudes toward obesity prevention identified more factors than initially assumed. The questionnaire is considered reliable as a tool for measuring adolescents' readiness for action and attitudes toward obesity prevention.

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Public health research and practice is increasingly employing systems thinking to help grapple with complex issues, from obesity to HIV treatment. At the same time, there is growing recognition that to address a given problem it is essential collaborate with those most at risk of or affected by it. Group model building (GMB), a process grounded in system dynamics, combines systems thinking and participatory methods to structure and address complex issues. As part of the CO-CREATE project we conducted GMB sessions with young people in six countries to create causal loop diagrams showing the factors that they believe drive obesity. This paper describes the background to GMB and the process we used to construct causal loop diagrams; it discusses how GMB contributed to generating noteworthy and useful findings, and the strengths and limitations of the method. Using GMB, we identified areas of concern to adolescents in relation to obesity that have so far had little attention in obesity research and policy: mental health and online activity. In using GMB, we also helped answer calls for a more participatory approach to youth involvement in research and policy development.

Background Capturing voices of young people on issues that affect them is crucial for developing effective, relevant public health policies. We report the use of group model building with young people to identify their views on drivers of adolescent obesity. This is the first stage of the Co-Create project, designed to develop-with adolescents-potential interventions to reduce obesity prevalence.Methods Co-Create uses an innovative, participatory, multi-staged methodology, underpinned by a systems approach. We followed a group model building script to generate causal loop diagrams, with 16-18-year-olds from three UK schools (mean number of participants per school 14), of factors perceived to contribute to diet and physical activity and, therefore, obesity. Schools were recruited using a sampling frame to represent three quartiles from the index of multiple deprivation ranking of local authorities.Findings All causal loop diagrams showed that participants identified advertising, the low cost of and easy access to unhealthy food, social media, lack of physical activity, and stress, body image, and other mental health factors as drivers of diet and physical activity and, therefore, obesity. There were no notable differences in themes between the causal loop diagrams.Interpretation Use of group model building, a participatory systems methodology, captures obesity drivers pertinent to young people, the ways these drivers are intertwined, and potential leverage points for action. This process creates a helpful abstraction from individual behaviour by drawing out system-level, rather than individual, drivers of obesity, although findings are limited to the perceptions of participants and these results represent only urban environments. The results from this first stage of the Co-Create project help generate system-level hypotheses on policy responses to obesity that resonate with young people. In subsequent Co-Create workstreams, adolescents will be recruited to explore interventions to be discussed with policy makers and other stakeholders. The potential effects of the co-created, obesity-related interventions will be simulated using systems dynamics modelling.Funding EU Horizon 20/20 research and innovation programme for Sustainable Food Security (grant agreement 774210). ContributorsWe declare no competing interests.