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Résumé (français)

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Résumé (anglais)

Obesity and physical inactivity are major risk factors for numerous chronic diseases, conditions, and early mortality. Healthy body weight and physical activity (PA) are also positively associated with health-related quality of life (HRQL). However, obesity and physical inactivity levels in Canadian youth and adults are high. This thesis comprises five studies exploring the burden of obesity and physical inactivity, focusing on HRQL. The first study assessed PA research productivity in Canada from 1990-2005. Canada produced approximately 5% of global PA research, 50% originating from Ontario, the biomedical and clinical areas accounting for 40% each; however, research in population health and health services was lacking. The second study used data from the Physical Activity Longitudinal Study (PALS), the 22-year follow-up of the 1981 Canada fitness Survey, to assess PA and obesity tracking from youth to adulthood. Over 80% of overweight/obese youth became overweight/obese adults, while the majority of overweight/obese adults had not been overweight/obese youth; almost all healthy weight adults had been healthy weight youth. PA did not track over 22 years. The third study used the PALS data to examine the long-term effect of youth BMI and PA on adult HRQL (SF-36), using dichotomized outcomes based on Canadian norms. Contrary to expectations, overweight youth were more likely than healthy weight youth to score at/above the norm in adult HRQL, especially in the mental health domains. Youth PA was not associated with adult HRQL. The fourth study used the same data to explore the youth BMI-adult HRQL relationship using continuous outcomes, by sex. Youth BMI was positively associated with mental HRQL in adult females only; no negative impacts emerged. The fifth study used the Canadian Community Health Survey (CCHS) Cycle 3.1 data to investigate the combined association of PA and BMI to HRQL among Canadian adults, including self-rated health, participation/activity limitation, and total disability days, by age and sex. Inactive individuals had increased odds of adverse HRQL, regardless of weight status; underweight, overweight, and obesity were of little consequence for active individuals. Collectively, these results help to better understand the health burdens created by the current epidemics of obesity and physical inactivity in Canadians throughout their lifespans.