Body mass index of Canadian children and youth, 2009 to 2011

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Based on their measured body mass index (BMI), 32% of Canadian children and youth aged 5 to 17 years were overweight or obese in 2009 to 2011.

Excess weight in childhood has been linked to a number of health problems and is a major public health concern. Overweight and obese children have a higher risk of type 2 diabetes, hypertension, poor emotional health and diminished social well-being.^{Note 1} Overall, 32% of Canadian children aged 5 to 17 had a BMI that classifies them as overweight or obese, while 66% had a normal BMI. When both sexes were combined there was no difference in the likelihood of being overweight or obese between 5 to 11 year olds and 12 to 17 year olds (Chart 1).

Chart 1
Distribution of household population aged 5 to 17, by body mass index norms^† and age group, Canada, 2009 to 2011

Description for Chart 1

Chart 1 Distribution of household population aged 5 to 17, by body mass index norms and age group, Canada, 2009 to 2011

There was no significant difference in the likelihood of being classified as overweight between sexes, however boys (15%) were significantly more likely to be obese than girls (8%). This appears to be a result of a higher prevalence of obesity in boys aged 5 to 11 (20%) than girls of the same age (6%) as older boys and girls show no significant difference in their rates of obesity. Boys aged 5 to 11 were also significantly more likely to be obese than boys aged 12 to 17 (11%) (Chart 2).

Chart 2
Distribution of household population aged 5 to 17, by body mass index norms^† and age group and sex, Canada, 2009 to 2011

Description for Chart 2

Chart 2 Distribution of household population aged 5 to 17, by body mass index norms and age group and sex, Canada, 2009 to 2011

About body mass index

Body mass index (BMI) is the ratio of a person's weight in kilograms divided by their height squared in meters (kg/m²). BMI can be interpreted using the following classification table based on the World Health Organization's BMI-for-age Growth References for children and adolescents aged 5 to 17 years.^{Note 2} This approach is thought to provide more accurate estimates than previous methods used to estimate the prevalence of overweight and obesity in the Canadian population.^{Note 3}

This classification system uses the following cut-offs^{Note 2}:

Table 1
Body mass index classification system
Less than or equal to 2 standard deviations below the mean	Thinness
Greater than 2 standard deviations below the mean and less than or equal to 1 standard deviation above the mean	Normal weight
Greater than 1 standard deviation and less than or equal to 2 standard deviations above the mean	Overweight
Greater than 2 standard deviations above the mean	Obesity

References

Roberts KC, Shields M, Groh MD, Aziz A, Gilbert JA. Overweight and obesity in children and adolescents: Results from the 2009 to 2011 Canadian Health Measures Survey. Health Reports. 2012;23(3):1-5.
de Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. Bulletin of the World Health Organization. 2007;85(9):660-7.
Analyses of cycle 1 of the CHMS, including previous versions of this fact sheet, used different BMI cut-off points. As a result, the estimates are not comparable.

For more information on the Canadian Health Measures Survey, please contact Statistics Canada's National Contact Centre (toll-free 1-800-263-1136; 613-951-8116; infostats@statcan.gc.ca).