Study design and rationale for TEENS+REACH: Evaluating ripple effects of a family-based lifestyle intervention to untreated family members.

Background: Understanding the effects of family-based lifestyle intervention beyond the treated adolescent is important, given that obesity is a familial disease and there are likely bidirectional relations between an adolescent's treatment success and broader household changes. However, it is unknown if recommended household-wide changes are adopted or if untreated family members experience weight-related benefits. Methods: TEENS + REACH leverages our ongoing randomized clinical trial of TEENS+, a family-based lifestyle intervention for adolescents with obesity, to determine: 1) if household-wide changes to the shared home environment are implemented, 2) if ripple effects to untreated family members are observed, and 3) whether these changes are predictive of adolescents' weight management success. TEENS + REACH will expand trial assessments to include comprehensive assessments of the shared home feeding, weight, and physical activity environment of the target adolescents. Specifically, we will enroll untreated children (8-17yrs) and caregivers living in the same household as the target parent/adolescent dyad (N = 60 families). At 0, 2, 4 (primary endpoint), and 8-months, the target parent/adolescent dyad and other untreated children and caregivers in the home will complete anthropometric assessments. Discussion: Results will determine the familial reach of TEENS+ and reveal potential mediators of treatment response, which can inform future efforts to optimize family-based lifestyle interventions. Trial registration: TEENS + REACH was retrospectively registered in Clinicaltrials.gov March 22, 2023 (NCT05780970) as an observational study ancillary to the TEENS + clinical trial, registered February 22, 2019 (NCT03851796).