Janis Fiedler (@fiejanis.bsky.social)

A Refined #Mobile #Health Intervention (SMARTFAMILY2.0) to Promote #PhysicalActivity and Healthy Eating in a Family Setting: Randomized Controlled Trial Background: Many #Mobile #Health (#mHealth) apps focus on promoting #PhysicalActivity (PA) and healthy eating (HE). However, there is limited empirical evidence regarding their effectiveness in initiating and sustaining behavior change, particularly among children and adolescents. Considering that behavior is influenced by social contexts, it is essential to take core settings like family dynamics into account when designing #mHealth apps. Objective: The purpose of this study was to further develop and refine the SMARTFAMILY (SF) #App targeting PA and HE in a collective family-based setting by enhancing design and usability, as well as by adding gamification aspects, #Health literacy, and just-in-time adaptive interventions to the first version of the #App. Methods: The SF2.0 #App, based on behavior change theories and techniques, was developed, implemented, and evaluated. The #App was used in a collective family setting, with family members using it individually and cooperatively. In a cluster-randomized controlled trial, the intervention group (IG) used the #App for 3 consecutive weeks, while the control group (CG) received no treatment. Primary outcomes included PA measured through self-reports and accelerometry, as well as self-reported fruit and vegetable intake (FVI) for HE. Secondary outcomes included intrinsic motivation, behavior-specific self-efficacy, and the Family #Health Climate. A follow-up assessment (T2) was conducted 4 weeks after the postmeasurement (T1) to assess intervention effects. Multilevel analyses were performed in R (R Foundation for Statistical Computing), considering the hierarchical structure of individuals (level 1) within families (level 2). Results: Overall, 55 families (28 CG, 105/209; 27 IG, 104/209 participants) were recruited for the study. In total, 3 families (3 CG, n=12) chose to drop out of the study due to personal reasons before T0. Overall, no evidence for meaningful and statistically significant increases in PA was observed in favor of the IG of our physically active sample. However, the #App elucidated positive effects in favor of the IG for FVI diary (T0-T1; P=.03), joint PA (T0-T1; P=.02 and T0-T2; P http://dlvr.it/TPqwwh