LB001-SUN: Behavioural and Environmental Factors Associated With Body Mass Index During Adolescence

Abstract

Rationale: The growing prevalence of overweight and obesity in adolescents is of great concern. The objective of this research was to assess the relationship between body mass index (BMI) and individual factors such as: dietary intake, physical activity and sedentary behaviours; and to assess the relationship between BMI and interpersonal factors such as: food availability and encouragement of activity. Methods:Aweb-based survey of physical activity and nutrition (WebSPAN2) was completed by 4360 adolescents in grades 7 to10 in Alberta, Canada. Results: Data analysis showed that there was a difference in the proportion of normal weight, overweight and obesity between boys and girls (c2 p < 0.001). Multiple linear regression analysis was used to examine the association between BMI and individual and interpersonal factors. Results of this analysis showed that, sex and grade level contributed significantly to the model (sex: b = 0.040, p = 0.047; grade level: b = 0.163, p < 0.001), with boys and students in higher grades more likely to have a higher BMI. Unexpectedly, we found that nutrition beliefs were positively associated with BMI (nutrition beliefs: b = 0.079, p < 0.00). Physical activity and sedentary behaviours were also significantly associated with BMI (physical activity: b = 0.069, p = 0.001; sedentary behaviours: b = 0.106, p < 0.001). Higher physical activity level was associated with lower BMI among adolescents; and the more time spent in sedentary behaviours was associated with higher BMI among adolescents. Other variables were not significant predictors of BMI. Conclusion: Results from this cross-sectional study suggest that insufficient physical activity and extended periods of time spent in sedentary behaviours were the only modifiable risk factors associated with a higher BMI of adolescents. Cohort studies are required to clarify the relative importance of individual and interpersonal factors on overweight and obesity during adolescence.