Recruiting and retaining young adults: What can we learn from behavioural interventions targeting nutrition, physical activity and/or obesity? A systematic review of the literature.

OBJECTIVE To describe strategies used to recruit and retain young adults in nutrition, physical activity and/or obesity intervention studies, and quantify the success and efficiency of these strategies. DESIGN A systematic review was conducted. The search included six electronic databases to identify RCTs published up to 6th December 2019 that evaluated nutrition, physical activity and/or obesity interventions in young adults (17-35 years). Recruitment was considered successful if the pre-determined sample size goal was met. Retention was considered acceptable if ≥80% retained for ≤6-month follow-up or ≥70% for >6-month follow-up. RESULTS From 21,582 manuscripts identified, 107 RCTs were included. Universities were the most common recruitment setting used in 84 studies (79%). Less than half (46%) the studies provided sufficient information to evaluate whether individual recruitment strategies met sample size goals, with 77% successfully achieving recruitment targets. Reporting for retention was slightly better with 69% of studies providing sufficient information to determine whether individual retention strategies achieved adequate retention rates. Of these, 65% had adequate retention. CONCLUSIONS This review highlights poor reporting of recruitment and retention information across trials. Findings may not be applicable outside a university setting. Guidance on how to improve reporting practices to optimise recruitment and retention strategies within young adults could assist researchers in improving outcomes.