Wearable activity tracker adherence associated with reduced body fat in a 12-month randomized trial

This randomized controlled trial enrolled 502 participants. The population consisted of 79.5% female individuals with a mean age of 45 years and a mean BMI of 33.7 kg/m. The setting was not reported. The study examined associations between wearable activity tracker adherence and changes in percent body fat and sex-specific waist circumference. The intervention involved adherence to goals of at least 300 minutes per week of moderate-to-vigorous physical activity (MVPA). The comparator was not reported as a separate arm, as the study examined associations within the full sample of participants randomized to standard monitoring or standard monitoring plus feedback. The follow-up period was 12.0 months.

Primary outcome results showed that greater MVPA adherence was associated with reductions in body fat in the full sample. The effect size was b = -0.01 with a 95% CI of -0.02, -0.005. When analyzing only completers, higher adherence was associated with decreases in body fat. The effect size was b = -0.01 with a 95% CI of -0.02, -0.004.

Secondary outcomes included waist circumference measurements stratified by sex. In the full sample, waist circumference in women was not associated with adherence. The effect size was b = -0.01 with a 95% CI of -0.03, 0.01. In men, waist circumference was also not associated with adherence in the full sample. The effect size was b = -0.03 with a 95% CI of -0.05, 0.0002. Among completers, higher adherence was associated with decreases in waist circumference for women. The effect size was b = -0.02 with a 95% CI of -0.04, -0.004. For men who completed the study, higher adherence was associated with decreases in waist circumference. The effect size was b = -0.04 with a 95% CI of -0.08, -0.003.

Safety and tolerability findings were not reported. Adverse events, serious adverse events, discontinuations, and overall tolerability were not reported. The study did not provide data on specific adverse event rates or discontinuation reasons.

These results support the use of wearable-derived physical activity measures in long-term mHealth behavioral interventions. The findings suggest that tracking adherence to MVPA goals may be linked to improvements in body fat percentage. However, the association with waist circumference was inconsistent across the full sample and only emerged in the completer subgroup for both sexes.

Key methodological limitations include the lack of reported setting details and the absence of a distinct comparator group for direct comparison. The study examined associations rather than establishing causality. The certainty of the evidence was not reported. Potential biases related to participant retention are suggested by the difference in results between the full sample and the completer analysis.

Clinical implications suggest that wearable technology can be a useful tool for monitoring physical activity in obesity management. The data supports using these devices to track adherence to MVPA goals. However, clinicians should interpret waist circumference results with caution as associations were not consistent in the full sample.

Questions remain unanswered regarding the specific mechanisms driving the reduction in body fat. It is unclear if the feedback component was the primary driver of adherence. Further research is needed to confirm these findings in diverse populations and to determine long-term sustainability of these effects.