Background: In Austria, around a quarter of children and adolescents and more than half of adults are currently overweight or obese. Treatment options include so-called multimodal group programmes consisting of nutrition, exercise and behavioural therapy. However, the providers of these programmes often have difficulties reaching their respective target groups and motivating them to participate (recruitment). Another challenge is "retaining" participants for the entire duration of the programme, i.e. achieving good programme adherence and avoiding early programme drop-outs. The aim of the report was to identify recruitment methods and strategies to improve programme adherence in multimodal group programmes for children, adolescents and adults with overweight or grade 1 obesity and to provide an overview of existing programmes in German-speaking countries.

Methods: Two systematic literature searches were conducted and primary studies (for the topic of recruitment) and reviews (for the topic of programme adherence) were included. The programmes in German-speaking countries were identified both by handsearching and by contacting experts.

Results: 16 studies of different study designs on recruitment and eight reviews on programme adherence were included. Numerous recruitment methods and strategies for improving programme adherence were reported in the studies included. It is usually recommended to combine several active and passive strategies to recruit target groups, e.g. referral by physicians with advertisements and media reports. To improve programme adherence, both programme-specific strategies (e.g. co-designing of programmes, easily accessible course locations) and generic strategies aimed at motivating participation (e.g. motivational interviewing combined with the strategy of self-observation) can be considered. Some targeted strategies were identified for vulnerable groups, such as recruitment in specific locations used by the target group, multilingual programme materials or subsidising co-payments. Numerous barriers at different levels were also reported, including fear of stigmatisation, lack of motivation and organisational factors (e.g. scheduling conflicts, care of siblings).

Conclusion: Due to the limitations of the literature considered, the results are not reliable evidence with a "guarantee of success", but rather a broad overview of options that can be applied depending on the framework conditions and target groups. Some of the strategies mentioned are already being implemented in existing programmes in Austria, Germany and Switzerland. The results can be used for the (further) development of programmes in order to improve recruitment processes and programme adherence.