Assessing physical activity and sedentary behaviour long-term post Roux-en-Y gastric bypass surgery

Over the past 30 years, the prevalence of obesity (BMI ≥ 30kg/m2) in Canada has increased 400 %. Even more concerning, the prevalence of Class III (BMI ≥ 40kg/m2) obesity has increased over 1000 % during the same period. Obesity is associated with type-2-diabetes, cardiovascular disease, depression, and musculoskeletal pain. These co-morbidities collectively cost the Canadian economy $ 4.3 billion per year in healthcare costs and lost productivity at work. Moreover, obesity results in mobility impairments including reduced stride length and slower walking cadence. For individuals living with extreme obesity and a related co-morbidity, bariatric surgery is the preferred treatment option. Bariatric surgery yields dramatic weight loss, resolution of most co-morbidities, reductions in pain, and improvements in physical functioning. Although these alterations are thought to yield more physical activity, to date, no changes in steps per day or sedentary time have been objectively measured from pre- to one-year post-surgery. After surgery, patients fail to meet established physical activity guidelines and begin to show small amounts of weight regain as early as two-years post-surgery.The first two manuscripts presented in this dissertation focused on evaluating the free-living movement patterns of individuals' long-term post-bariatric surgery (steps, sedentary time, and cadence), and determining if these patterns affect weight regain. It was found that patients do not step enough (6375 ± 2690 steps/day), are excessively sedentary (9.7 ± 2.3 hrs/day), and walk at significantly slower speeds on weekends compared to weekdays. As the built environment plays a role in physical activity and sedentary time on a population scale, it became important to assess if these constructs had the same effect on the bariatric population. Therefore, the third and fourth investigations evaluated the effect of neighbourhood walkability and employment status on physical activity, sedentary time, and weight regain respectively. These investigations proved that the built environment does not affect activity habits or obesity severity in the bariatric population. As substantial weight loss from surgery and aspects of the built environment have failed to promote physical activity and limit sedentary time, it is apparent that self-monitoring in this population is important. Therefore, the final investigation of this dissertation examined the validity of inexpensive, commercially available physical activity monitors against a research-grade accelerometer. This study showed that FitbitTM activity monitors are effective measurement tools for monitoring daily steps and time spent in light intensity activities. This confirmation allows bariatric surgeons to prescribe these activity monitors with confidence and can help patients self-monitor, meet established physical activity guidelines, and avoid weight regain post-surgery.This thesis was the first to objectively monitor physical activity and sedentary time long-term post-bariatric surgery. These studies filled important gaps in the literature related to the effects of the built and occupational environments on physical activity, sedentary habits, and weight regain post-surgery. Future studies should evaluate the effectiveness of interventions pre- and post-surgery designed to reduce and break up extended periods of sedentary time, while simultaneously promoting walking through light intensity activities. Interventions should employ the use of inexpensive commercially available activity monitors to improve self-monitoring, which can help individuals to meet established national activity guidelines.

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