The 2009 to 2011 Canadian Health Measures Survey provides the most recent measured body mass index (BMI) data for children and adolescents. However, different methodologies exist for classifying BMI among children and youth. Based on the most recent World Health Organization classification, nearly a third of 5- to 17-year-olds were overweight or obese. The prevalence of obesity differed between boys and girls (15.1% versus 8.0%), most notably those aged 5 to 11, among whom the percentage of obese boys (19.5%) was more than three times that of obese girls (6.3%). These estimates indicate a higher prevalence of overweight/obesity among children than do estimates based on International Obesity Task Force cut-offs. Although the prevalence of overweight and obesity among children in Canada has not increased over the last decade, it remains a public health concern, given the tendency for excess weight to persist through to adulthood and lead to negative health outcomes.