International definitions of overweight and obesity for children: a lasting solution?

Background: Definitions of overweight and obesity for children were published in 2000, derived by averaging the centiles of six countries equivalent to body mass index (BMI) at age 18 years of 25 and 30. For use in the UK it is unclear whether these present an advantage over equivalent definitions based on UK data. Aim: To compare the recently published international cut-off points for overweight and obesity in children with alternative cut-off points based on the UK 1990 reference data. Subjects and methods: Around 6000 white children aged 4-11 years from primary schools in 22 areas in England were measured in two cross-sectional surveys, in 1984 and 1994. Measurements included height and weight, from which BMI was calculated. Each child was classified as overweight or obese according to each cut-off point. Results: The proposed international cut-off points exaggerate the difference in prevalence of overweight and obesity between English boys and girls in comparison to comparable measures based on UK data by up to 7%, and are not compatible with the UK reference charts for BMI. Using proposed UK cut-off points the prevalence of overweight in boys was 10.2% in 1984, rising to 13.8% in 1994, compared to 5.4 to 9.0% using the international definition. Conclusion: The limitations of the international definitions, due to averaging data from different countries and the choice of reference age, need to be known. The UK cut-off points here presented are compatible with the current UK reference curves.