Definitions of childhood obesity: current practice

To review current practice in the definition of childhood obesity based on body mass index (BMI), in order to understand why the recommendations of the International Task Force on Obesity (IOTF) have not been fully adopted.

Literature search using MEDLINE to identify papers on childhood obesity published in the first 4 months of 2005, and a cited reference search on the recommendations of the IOTF.

Citations of the IOTF definition have increased since publication, but less than half of papers on childhood obesity published in the period used the definition. Most used the 95th centile of a national distribution to define obesity.

Reasons for using centiles of a national distribution included the need for z-scores or centiles to define underweight or extreme obesity, not available in conjunction with the IOTF definition, inclusion of children under 2 years, and concerns about over- or underestimation of the prevalence of obesity. None of these preclude use of the principle underlying the IOTF definition, that of continuity with the adult definition of BMI of 30 kg/m2 or more. Adoption of either the IOTF definition or corresponding centiles of a national distribution would enable comparisons of prevalence between countries and over time.