Effects of a Physical Activity mHealth Intervention (Fit2Thrive) on WCRF/AICR Cancer Prevention Recommendations among Breast Cancer Survivors: A Secondary Data Analysis.

Background: Interventions targeting moderate-to-vigorous physical activity (MVPA) may be a catalyst for improving other lifestyle behaviors in breast cancer survivors (BCS). We examined whether Fit2Thrive, an mHealth MVPA intervention, influenced adherence to cancer prevention recommendations.

Methods: BCSs (N = 269; age, mean = 52.9; SD = 9.9) received a 12-week mHealth MVPA intervention and were randomized to "on" or "off" level of five intervention components. The World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) score was calculated (0 = high cancer risk, 6 = low cancer risk) based on cancer prevention recommendations: sugar-sweetened beverages, fast food, fruit/vegetable intake, body mass index, alcohol consumption, and MVPA (baseline, 12 weeks, and 24 weeks). Mixed-effects models examined changes in the WCRF/AICR score and each risk factor and the effects of each intervention component (telephone support calls, Fitbit Buddy, tailored text messages, deluxe app, online gym) level on the WCRF/AICR score.

Results: The WCRF/AICR total score significantly improved at 12 and 24 weeks (P values < 0.001). MVPA improved at 12 and 24 weeks (P values < 0.001). Fruit and vegetable consumption improved at 12 weeks (P = 0.01). No changes in other risk factors were observed.

Conclusions: Participation in a mHealth MVPA intervention may influence cancer risk in BCS and have effects on certain untargeted behaviors (fruit and vegetable consumption) but not on other risk factors (sugar-sweetened beverages, fast food, body mass index, alcohol consumption). Future work should explore how to maximize these effects and determine if resource-efficient dietary intervention components improve cancer outcomes.

Impact: Understanding the impact of an mHealth MVPA intervention on untargeted dietary behaviors may guide the development of scalable interventions targeting lifestyle behaviors.