Understanding and influencing the maintenance of physical activity and dietary behaviour change in breast cancer survivors

Abstract

Background: Maintaining improvements in health behaviours following an intervention is necessary for optimal long-term health outcomes. Extending contact with participants following an initial intervention has been shown to promote maintenance of behaviour change and thus weight loss. Mobile telephone text messaging may be an ideal delivery modality to provide such extended contact. The Living Well after Breast Cancer feasibility weight loss trial provided the opportunity to evaluate a novel text message-delivered extended contact intervention. Aims and objectives: The primary aim of this thesis was to evaluate the feasibility, acceptability, and efficacy of a text message-delivered extended contact intervention in promoting the maintenance of weight loss and physical activity and dietary behaviour change. Four studies comprised this thesis research. Study One was a systematic review of maintenance outcomes following physical activity and/or dietary behaviour change interventions in breast cancer survivors. Study Two was a text message-delivered pilot study that informed the development of Study Three, the Living Well after Breast Cancer extended contact intervention. Study Four explored the predictors associated with short- and long-term physical activity and dietary behaviour change during the intervention. Methods and Results: Study One: A systematic review of physical activity and/or dietary behaviour change interventions in breast cancer survivors was conducted to determine the frequency with which physical activity and dietary maintenance outcomes are reported, and the participant and intervention characteristics associated with successful maintenance outcomes. A structured search of a range of relevant databases yielded a total of 1,298 publications, of which 63 trials were included. Findings indicated few trials reported on post-intervention outcomes (16%), and of those, less than half reported successful maintenance (40%). Few intervention characteristics were identified due to the heterogeneity of studies. Attention needs to be directed towards reporting post-intervention outcomes to inform extended contact intervention development. Study Two: A pilot study was conducted to determine the acceptability and feasibility of sending text messages to breast cancer survivors. Eight participants (mean age = 49 years) received highly tailored text messages to support physical activity and dietary behaviour change for two weeks. Participants reported high satisfaction, and reported the messages were encouraging and helpful reminders for behaviour change. The intervention was feasible to deliver on a small scale. These pilot findings informed the development of the Living Well after Breast Cancer extended contact intervention. Study Three: The feasibility, acceptability, and efficacy of the Living Well after Breast Cancer extended contact intervention to promote the maintenance of weight loss and physical activity and dietary behaviour change was evaluated. Participants completed an initial six-month telephone-delivered weight loss intervention (baseline to 6-months), and a six-month text message-delivered extended contact intervention (6- to 12-months), which was followed by a six-month period of no-contact (12- to 18-months). Guided by Social Cognitive Theory, text messages targeted a range of constructs and strategies proposed to be important for maintenance of weight loss and behaviour change. Text messages were individually tailored to participant preferences for timing, content, and frequency. Participants at baseline (n = 29) had a mean (SD) age of 55 (8.8) years, BMI of 30.0 (4.2) kg/m2, and were recruited a mean of 16.6 (3.2) months post-diagnosis. From baseline to 18-months, participants showed statistically significantly lower mean (95% CI) weight (-4.2kg [-6.0kg, -2.4kg]; p<0.001) and higher physical activity levels (10.4mins/day [3.6mins/day, 17.2mins/day]; p = 0.003), but no significant differences in energy intake (p = 0.200). Participants elected to receive a mean of eight text messages per fortnight (range 2-11), and reported a high rate of satisfaction. Results suggested a text message-delivered extended contact intervention may support the attenuation of weight regain and promote the maintenance of physical activity. Study Four: This study evaluated the theoretical constructs and participant characteristics associated with short- and long-term physical activity and dietary behaviour change in participants who completed the Living Well after Breast Cancer extended contact intervention. Findings indicated the importance of comprehensively targeting individual, social, and environmental constructs to promote short- and long-term behaviour change. Specifically, self-efficacy was associated with short- and long-term physical activity change, outcome expectancy and perceived environmental opportunity were associated with long-term physical activity change, and social support was associated with short- and long-term dietary change. Participants who were not employed, did not receive endocrine treatment, and were more than 12-months post-treatment were most responsive to the intervention. These findings fill a current gap in the literature identifying underlying behaviour change mechanisms that drive maintenance of behaviour change. Conclusion: This thesis research makes an important contribution to the limited evidence on the development, delivery, and evaluation of interventions to promote maintenance of physical activity and dietary behaviour change. Randomised trials are needed to evaluate comparative-effectiveness and cost-effectiveness of extended contact intervention delivery modalities to promote long-term weight loss and behaviour change.