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Obesity in Canadian children
See response from: M. Tremblay, J.D. Willms
Mark Tremblay and Douglas Willms have reported that the prevalence of overweight increased from 15% in 1981 to 35.4% in 1996 among Canadian boys aged 713 years and from 15% to 29.2% among Canadian girls aged 713 years [Research].1 The prevalence of obese children tripled over that period, from 5% in 1981 to 16.6% for boys in 1996 and from 5% in 1981 to 14.6% for girls in 1996.1 The values reported by the authors are interesting in that they clearly show an increase in overweight and obesity over time; however, it must be kept in mind that overweight and obesity were arbitrarily defined as the 85th and 95th percentiles respectively of the 1981 Canada Fitness Survey sample.
It was recently proposed that definitions of overweight and obesity corresponding to the health-related cut-offs used in adulthood (25 kg/m2 and 30 kg/m2 respectively) be developed for children and youth.2 These cut-offs were recently derived using LMS regression by passing a line through the adult cut-off values at age 18 years for a large international sample.3 Theoretically, these values may be more comparable to the established adulthood cut-offs than arbitrarily defined percentile cut-offs and could also be used as a yardstick for international comparisons. The prevalences of overweight and obesity calculated using the adult health-related definitions are lower than the arbitrarily defined values of 15% and 5% (Table 1). In fact, the prevalence of obesity is less than half of 5% in both boys and girls. The prevalences of obesity in the 1996 National Longitudinal Study of Children and Youth are also somewhat lower than those reported by Tremblay and Willms.
The trends for overweight and obesity among Canadian children determined using the new health-related international cut-offs are the same as those reported by Tremblay and Willms, but use of these cut-offs will better allow comparisons to be made between countries and between children and adults.
I thank Cora Craig and her colleagues at the Canadian Fitness and Lifestyle Research Institute for providing data from the 1981 Canada Fitness Survey, and Lecily Hunter of the National Longitudinal Study of Children and Youth Project, Special Surveys Division, Statistics Canada, for providing data analyses on the National Longitudinal Study of Children and Youth master file.
Peter T. Katzmarzyk