Adolescent obesity is a complex public health challenge with steadily increasing and variable prevalence among countries. This paper synthesises the driving feedback mechanisms of adolescent obesity studied in the CO-CREATE project, furthering our understanding of the complexity of this issue. Using systems thinking principles and causal loop diagramming, we integrated the following knowledge and perspectives derived from diverse sources into a causal loop diagram (CLD): a systems map generated by adolescents through participatory modelling workshops, a comprehensive literature review, and input from subject-matter experts during validation workshops. We used a structured and iterative approach to include drivers and to identify feedback loops exacerbating adolescent obesity. The CLD identified 27 key feedback loops across four themes: twelve related to the commercial food environment, six to the physical activity environment, four to mental wellbeing and five to social norms. These loops indicate not only diet and physical activity as drivers of obesity but also stress and other emotional and social pressures. Recognising the imperative need to integrate the perspectives and experiences of adolescents into our analysis, this work advocates for the synthesis of experiential insights with empirical research. The integrated CLD can be used as a visual tool that fosters collaboration among stakeholders and engenders a more comprehensive and inclusive system understanding that can provide holistic intervention considerations to tackle adolescent obesity. Additionally, the CLD lays a foundation for subsequent quantitative modelling works to further address this issue and develop context-based approaches to prevention and evaluation of adolescent obesity.