Long-term Follow-up After Childhood Obesity

The goal of this observational study is to learn about the long-term effects on health and well-being of treatment for overweight in childhood or adolescence using the Children's Obesity Clinic Treatment protocol (the Holbæk Model) (HM). The study has two parts: * An active follow-up study, where participants are invited to take part in new measurements and questionnaires * A register-based study, which uses existing data on diagnoses, medication use, and school well-being The submitted protocol primarily focuses on the active follow-up study. The register-based study covers diagnoses, medication use, and school-related well-being and is described in the section "Detailed description". In the active follow-up study, researchers will examine: * Body measurements such as height, weight, and waist circumference * Body composition * Psychosocial well-being and mental health * Eating behaviors in young adults Participants will be followed for up to 20 years after treatment initiation. Where possible, results will be compared with a group of people of the same age from the same area who did not receive this treatment. This will help show whether their development differs from that of the general population. The aim is to use the findings to improve future follow-up care and support for people who were treated for overweight as children. The study includes two groups: 1. A treatment group of individuals treated at the Holbæk Pediatric Department between 2008 and 2025 2. A comparison group from the general population, recruited between 2010 and 2016 The study will take place in two phases: * A pilot phase (about 1.5 years) to test procedures and recruitment * A main phase (about 3 years) Participants are invited to one follow-up visit. During this visit: * Body measurements will be taken * Body composition will be assessed * Participants will complete questionnaires The study team will ensure that all participants are treated respectfully and without stigma. Flexible options, including home visits, are offered to make participation easier.