The "Stages Towards Completion Model": what helps and hinders children with overweight or obesity and their parents to be guided towards, adhere to and complete a group lifestyle intervention.

: Lifestyle interventions can be effective in the management of overweight and obesity in children. However, ineffective guidance towards interventions and high attrition rates affect health impacts and cost effectiveness. The aim of this study was to gain insight into the factors influencing participation, in particular guidance towards, adherence to and completion of an intervention.: A narrative literature review was performed to identify factors related to participation, leading to the development of the "Stages towards Completion Model". Semi-structured interviews (n = 33) and three focus group discussions (n = 25) were performed with children and parents who completed two different group lifestyle interventions, as well as with their coaches.: The main barrier to participating in a lifestyle intervention was the complex daily reality of the participants. The main facilitator to overcome these barriers was a personal approach by all professionals involved.: Participation in a lifestyle intervention is not influenced by one specific factor, but by the interplay of facilitators and barriers. A promising way to stimulate participation and thereby increase the effectiveness of interventions would be an understanding of and respect for the complex circumstances of participants and to personalize guidance towards and execution of interventions.