A longitudinal analysis of physical activity and overweight/obesity in adolescents in Saskatoon

Overweight and obesity, one of the most common public health problems in affluent societies, have become epidemic not only in Canada but also throughout the world. Obesity is also a major contributor to the global burden of chronic disease and disability such as diabetes, hypertension, and cardiovascular disorders. Studies have demonstrated clearly that higher intake of cholesterol and saturated fats and generally higher intake of energy-dense food are a key determinant of increasing levels of obesity and overweight in children. Physical activity is also recognized as a major factor in preventing obesity among children. Environmental factors—by which we mean both social (such as social support, social networks) and physical environment (such as access to physical activity amenities, roads and trails, grocery stores)—in generally believed to have a powerful influence on either limiting or enhancing the effects of fundamental determinants (diet and physical activity) of obesity in children. This thesis focuses on one of the key determinants, physical activity, and in turn examines factors that are related to changing physical activity in children. This research was designed to examine two major questions: (1) How do physical activity and overweigh/obesity change over time in a cohort of adolescents in Saskatoon? Are there differences in the patterns of change in overweight/obesity and physical activity between boys and girls? (2) What are the effects of family/friends and physical environments on the changing patterns of physical activity in this sample? The data used in this study was taken from the in motion studies’ longitudinal data. Study participants include 837 adolescents from12-18 years of age from two high schools and five elementary schools from two diverse geographic areas in Saskatoon (low and high socioeconomic status). Physical activity patterns of adolescents were investigated over a five-month period (e.g., type, frequency, and duration). Participants were also asked to respond to questions on demographics, social support, perceived benefits and barriers of physical activity, and health practices. The results of this study indicated that overweight/obesity increased with age, while physical activity decreased with age for both boys and girls. Boys overall were more likely to be physically active than were girls. Adolescents who received greater direct support from family members were 21% more likely to sustain their physical activity levels (relative odds 1.21; 95% CI 1.17, 1.24); in contrast, the more the family’s indirect support the 5.4% less sustaining were the adolescents’ physical activity (relative odds 0.94; 95% CI 0.91, 0.98). Home environments which were ‘rich’ in resources relevant to physical activity had 4% greater influence on adolescents’ physical activity levels, and this relationship was stronger than that of the influence of living in certain neighbourhoods (relative odds 1.04; 95% CI 1.03, 1.05). This research shed some greater understanding of the impact of family’s support and physical environment factors on adolescents’ continued physical activity levels. The implications of results for further research, targeted programs, and social policy is discussed in the thesis