A systematic review of the dose-response relationship between usage and outcomes of online physical activity weight-loss interventions

Online physical activity interventions can be an effective strategy for weight loss. However, there is a lack of systematic reviews examining the relationship between intervention usage (dose) and participants' response to online physical activity interventions for weight loss. It remains unclear whether certain usage metrics (e.g. login frequency, percent of content accessed) would be associated with improvements in behavioral outcomes. Understanding the dose-response relationship for online physical activity interventions for weight loss would be important for designing and evaluating future interventions. 1) Review the methods used to assess intervention usage and 2) to explore the association between intervention usage metrics and outcomes for online physical activity interventions for weight-loss. We conducted a systematic review following the PRISMA guidelines to examine the dose-response relationship of online-based interventions targeting physical activity. We used the following keywords: web OR internet OR online OR eHealth AND physical activity OR exercise, AND engagement OR dose OR dose-response OR usage AND obesity OR weight*. Peer-reviewed articles published between 2006 and 2019 were included. A total of five articles met the inclusion criteria. The mean intervention length was 10 ± 6 months (range 2–30 months). The usage metrics were total number of logins, login frequency, and usage of online tools. All usage metrics reported were found to be related to outcomes in physical activity interventions for weight-loss. Our findings suggest that usage metrics for online physical activity interventions for weight-loss included login frequency, login duration, and use of online tools. Increased intervention usage appeared to be associated with an improvement in participant's weight, physical activity behaviors, and intervention retention. Future research should examine innovative ways to maintain intervention usage throughout the intervention. •There are few studies examining the dose-response relationship of online physical activity interventions for weight-loss•Usage metrics for evaluating dose-response relationships included login frequency, login duration and use of online tools•Most usage metrics reflected time spent interacting with an intervention but not the quality of interaction•Increased intervention usage appeared to be associated with improvements in outcomes•Further studies examining usage metrics are needed to better understand dose-r