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Background: Numerous smartphone apps are targeting physical activity and healthy eating, but
empirical evidence on their effectiveness for initialization and maintenance of behavior change,
especially in children and adolescents, is still limited.
Objective: The aim of this study was to conceptualize a theory-based and evidence-based mHealth
intervention called SMARTFAMILY (SF) that targets physical activity and healthy eating in a collective
family-based setting. Subsequently, the app will be refined and re-evaluated to analyze additional
effects of just-in-time adaptive interventions (JITAIs) and gamification features.
Methods: A smartphone app based on behavior change theories and behavior change techniques
was developed and implemented and will be evaluated with family members individually and
cooperatively (SF trial). Existing evidence and gained results were used to refine and will be used to
re-evaluate the app (SF2.0 trial). Both trials are cluster randomized controlled trials with 3
measurement occasions. The intervention group uses the app for 3 consecutive weeks, whereas the
control group receives no treatment. Baseline measurements (T0) and postintervention
measurements (T1) include physical activity (ie, self-reported and accelerometry) and healthy eating
measurements (ie, self-reported fruit and vegetable intake) as the primary outcomes. The secondary
outcomes (ie, self-reported) are intrinsic motivation, behavior-specific self-efficacy, and the family
health climate, complemented by an intentional measure in SF2.0. Four weeks following T1, a follow-
up assessment (T2) is completed by the participants, consisting of all questionnaire items to assess
the stability of the intervention effects. Mixed-method analysis of covariance will be used to
calculate the primary intervention effects (ie, physical activity, fruit and vegetable intake) while
controlling for covariates, including family health climate, behavior-specific self-efficacy, and intrinsic
motivation.
Results: This study is funded by the German Federal Ministry of Education and Research and ethically
approved by the Karlsruhe Institute of Technology. For both trials, it is hypothesized that the apps
will positively influence physical activity and healthy eating in the whole family. Furthermore, SF2.0 is
expected to produce stronger effects (ie, higher effect sizes) compared to SF. SF app development
and piloting are completed. Data acquisition for the SF trial is terminated and discontinued due to
the COVID-19 pandemic. SF2.0 app development and piloting are completed, while data acquisition is
ongoing. Participant recruitment for the SF 2.0 trial started in February 2020. The results for SF are
expected to be published in mid-2021, and the results of SF2.0 are expected to be published in mid-
2022.

Conclusions: In this study, it is hypothesized that targeting the whole family will facilitate behavior
change at the individual level and the family level, as the implemented strategies address changes in
daily family life. Furthermore, subsequent app development (SF2.0) with supplementary addition of
motivation-enhancing features and a JITAI approach is expected to enhance positive intervention
effects.

Bibliographic information:

Wunsch, K., Eckert, T., Fiedler, J., Cleven, L., Niermann, C., Reiterer, H., Renner, B., & Woll, A. (2020)
Effects of a Collective Family-Based Mobile Health Intervention Called “SMARTFAMILY” on Promoting
Physical Activity and Healthy Eating: Protocol for a Randomized Controlled Trial. JMIR Res Protoc,
9(11):e20534, doi: 10.2196/20534 PMID: 33174849 PMCID: 7688389