Summary The CO‐CREATE project aims to collaborate with adolescents across Europe in developing policy ideas that contribute to overweight and obesity prevention. In this paper, we present the theoretical basis and methodological approach to recruitment and engagement in the project. The principles of youth‐led participatory action research were employed to design Youth Alliances in which adolescents and adults could collaborate. These Alliances should serve to promote and support adolescent participation and to develop policy ideas that would contribute to obesity prevention. Alliance members were recruited in two local geographical areas per country with a focus on reaching out to underrepresented youth. We started with fieldwork to assess locally relevant forms of inclusion and exclusion. The methodology entailed a handbook combining existing tools which could be used flexibly, a collaborative organization, and budgets for the alliances. Engagement started in local organizations, that is, schools and scouts, and with peers. Health‐ and overweight‐related challenges were addressed in their immediate surroundings and supported the inclusion of experiential knowledge. Adolescents were then supported to address the wider obesogenic system when designing policy ideas. The CO‐CREATE Alliances provide a concrete example of how to engage youth in public health, in a manner that strives to be participatory, transformative, and inquiry based.

Hymenoplasty is surgery to alter the shape of the hymen membrane in the vaginal canal, commonly performed to minimise the aperture. This medical operation is often requested by women who expect that their virginity will be under scrutiny, particularly during their first sexual encounter on their wedding night. Despite increasing demand for the surgery all over the globe, there is no one standard of practice in performing hymenoplasty. In the Netherlands, the manner in which medical consultations concerning the procedure take place depends heavily on the consulting physician. This paper looks at two different approaches to hymenoplasty consultation in the Netherlands: a pedagogical philosophy adopted in a public hospital and a practical approach employed by a private clinic. Each approach culminates in a contrasting result: patients in one medical establishment are twice as likely to undergo hymenoplasty than those visiting the other.

Engaging youth in obesity prevention research and policy action is essential to develop strategies that are relevant and sensitive to their needs. Research with young people requires critical reflection to safeguard their rights, dignity, and wellbeing. The CO-CREATE project used various methods to engage approximately 300 European youth aged 15-19 years in the development of policies to prevent adolescent obesity. This paper discusses ethical considerations made in the project pertaining to the youth's voluntary participation, their protection from obesity stigma, respect for their time, data privacy and confidentiality, power balance, and equality of opportunity to participate in the research. We describe measures implemented to prevent or limit the emergence of ethical challenges in our interaction with youth and discuss their relevance based on our experience with implementation.While some challenges seemingly were prevented, others arose related to the youth's voluntary participation, time burdens on them, and the sustainability of participation under the Covid-19 pandemic. Concrete and ongoing ethical guidance may be useful in projects aiming to interact and build collaborative relationships with youth for long periods of time.

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.

This paper provides new perspectives on the scholarship on medicalization and demedicalization, building on an ethnography of hymenoplasty consultations in the Netherlands. By examining how doctors can play an active role in demedicalization, this paper presents novel insights into Dutch physicians' attempt to demedicalize the "broken" hymen. In their consultations, Dutch doctors persuade hymenoplasty patients to abandon the assumed medical definition of the "broken" hymen and offer nonmedical solutions to patients' problems. Drawing from unique ethnographical access from 2012 to 2015 to 70 hymenoplasty consultations in the Netherlands, this paper's original contribution comes from closely examining how demedicalization can be achieved through the process of medicalization. It investigates how Dutch physicians go even further in their efforts to demedicalize by medicalizing "cultural" solutions as an alternative course of action to surgery.