Of the 291 public schools in Nova Scotia with grade 5 classes, 282 (96.9%) participated in the study. Parental consent was received for 5517 students, which provided an average response rate of 51.1% per school. One of the 7 provincial school boards did not allow measurements of height and weight. Students without height and weight measurements were excluded from the analyses, leaving a sample of 4298 children from 242 schools.
The prevalence of overweight among grade 5 students in Nova Scotia in 2003 was 32.9%, with 9.9% being obese. The prevalence of overweight was about the same for girls (32.9%) and boys (33.0%), whereas the prevalence of obesity was lower among girls (9.0%) than among boys (10.9%).
Among grade 5 students, 3.7% did not eat breakfast (). In a univariate analysis, these students were 1.5 times (or 50%) more likely to be overweight than students who usually ate breakfast. Missing lunch was also associated with an increased risk of excess body weight, but this risk was not statistically significant. Relative to those bringing their lunch from home, children buying lunch at school were 47% more likely to be overweight (unadjusted odds ratio [OR] 1.47, 95% confidence interval [CI] 1.23–1.76). Increasing frequencies of eating supper together at home (family supper) and decreasing frequencies of eating supper in front of the television were associated with a decreased risk of overweight. Because dietary habits are interrelated, we considered these habits simultaneously and found that lunch pattern and frequency of family supper and supper in front of the television were determinants of body weight (: theme-adjusted ORs). After adjusting for all significant risk factors across all 4 theme groups, only buying lunch at school significantly increased the risk of overweight, and family suppers both 3–4 and 5 or more times a week significantly decreased the risk (: fully adjusted ORs).
Sedentary activity of more than 1 hour per day was associated with a significantly increased risk of overweight, as was being driven to school longer than 30 minutes (: theme-adjusted ORs). Participating in physical activity more than 7 times a week was associated with a decreased risk of overweight (: theme-adjusted ORs). When considered in conjunction with other determinants, frequency of physical activity appears to be the only activity-related factor independently associated with overweight. However, sedentary activity was independently associated with overweight when physical activity was not considered (data not shown), which indicates a correlation between these 2 covariates.
With respect to sociodemographic factors, children whose parents had attained higher levels of education and had an income over $60 000 were at a decreased risk of overweight, as were children who resided in urban areas and who resided in neighbourhoods where the income was in the middle or highest one-third ().
Of all children, 29.3% attended schools where lunches were provided by a foodservice company. This may include on-site catering or fast food delivery. Children attending such schools were 12% more likely to be overweight than children who attended schools where no foodservice companies were used, but this difference was not statistically significant (). Also, no substantial or statistically significant differences were observed among children attending schools where lunches were distributed by staff and volunteers or as part of a prepaid lunch program.
Of all children, 15.3% attended schools where soft drinks were sold. These children drank an average of 4.0 cans of soda pop per week compared with 3.6 cans drunk by children attending schools without such sales (p < 0.01). Children from schools with and without sales of soft drinks consumed an average of 33.5 and 32.5 g of sucrose per day respectively (p = 0.11). Availability of soft drinks at schools was not associated with significantly increased risks of overweight ().
Children attending schools with more frequent physical education classes were increasingly more likely to have normal body weight. Financial restraints on the purchase of recreation and gymnasium equipment were not statistically associated with increased weight ().
When we compared obese with normal-weight children, we obtained a model that identified male sex as a significant risk factor for obesity (). As well, the effects of parents' educational attainment, neighbourhood income, and frequency of physical activity and physical education classes were more pronounced for obesity than for overweight.