Definitions of pediatric obesity

Neither the article by Patricia Canning and associates¹ concerning prevalence of overweight and obesity among children in Newfoundland and Labrador nor the accompanying editorial by Douglas Willms,² noted that prevalence estimates vary according to the reference population.³ Canning and associates¹ used a classification developed by Cole and colleagues,⁴ who calculated body mass index (BMI) cut-off values for “overweight” and “obese” on the basis of height and weight measurements for about 100 000 children in Brazil, Great Britain, Hong Kong, the Netherlands, Singapore and the United States. Another common reference that is used for evaluating pediatric categories of “at risk of overweight” (BMI at or above the 85th percentile) and “overweight” (BMI at or above the 95th percentile) is a set of growth charts developed by the US Centers for Disease Control and Prevention.⁵ The latter reference was derived from height and weight measurements for US children collected over several decades as part of national nutrition and health examination studies.

The Dietitians of Canada, the Canadian Paediatric Society, the College of Family Physicians of Canada and the Community Health Nurses Association of Canada⁶ recently recommended that the Cole and colleagues⁴ reference be used for group (national or international) comparisons and the CDC reference⁵ be used for monitoring the growth of individual children. To our knowledge, only one study⁷ has compared prevalence estimates of overweight obtained with these 2 methods; given this paucity of research, the Canadian recommendations⁶ were based on expert opinion rather than scientific evidence.

It is important to acknowledge that height and weight data for Canadian children were not included in either reference; this lack of Canadian data is particularly relevant to the situation for Aboriginal youth. Although available data show that many Aboriginal preschool and grade-school children are overweight on the basis of a non-Aboriginal reference,⁸ the validity of this approach has been questioned, since the growth pattern of many indigenous populations worldwide has not been studied.⁹

Until nationally representative data on measured height and weight (including Aboriginal children) are available, Canadian researchers and health professionals alike must rely on comparisons with references that may not be representative of our children because of our geographic, cultural or ethnic uniqueness.

Geoff D.C. Ball Assistant Professor of Pediatrics Director, Pediatric Obesity Program Noreen D. Willows Assistant Professor of Community Nutrition Department of Agricultural, Food and Nutritional Science University of Alberta Edmonton, Alta.