Intended for healthcare professionals

Practice ABC of obesity

Childhood obesity

BMJ 2006; 333 doi: (Published 07 December 2006) Cite this as: BMJ 2006;333:1207
  1. John J Reilly, professor of paediatric energy metabolism1,
  2. David Wilson, senior lecturer2
  1. 1University Division of Developmental Medicine, Yorkhill Hospitals, Glasgow
  2. 2Division of Child Life and Health, University of Edinburgh, Royal Hospital for Sick Children, Edinburgh

    This article summarises recent evidence based clinical guidelines and systematic reviews and proposes strategies for managing paediatric obesity

    Obesity, an excessive body fat content with increased risk of morbidity, has become increasingly common in children and adolescents. Confusion exists, however, over basic questions such as whether paediatric obesity matters, how to diagnose it, and whether it should be treated (and if so, how best to do this). Doctors in many fields need a better understanding of these issues.

    Simplified diagram of some body mass index curves seen on UK BMI charts for boys (that for girls is similar). The charts are available from Harlow Health via the Child Growth Foundation (


    This is the 11th article in the series

    Subjective assessment methods are inaccurate, so diagnosis must be objective. A substantial and consistent body of high quality evidence has shown that body mass index (BMI; weight in kilograms divided by height in metres squared) can be used to diagnose obesity effectively.

    BMI is lower in childhood and adolescence than in adulthood and differs between boys and girls. Clinically, no diagnostic alternative exists, therefore, to considering BMI in an age and sex specific manner, either by plotting it on a BMI chart or by referring to tables of BMI for age and sex.

    Evidence based definitions of paediatric obesity

    For research and epidemiological purposes
    • Overweight should be defined as BMI ≥85th centile for sex and age

    • Obesity should be defined as BMI ≥95th centile for sex and age

    For clinical purposes in UK
    • Overweight should be defined as BMI ≥91st centile if using the UK BMI charts

    • Obesity should be defined as BMI ≥98th centile if using the UK BMI charts

    In the United Kingdom, BMI for age charts represent the distribution of BMI in children in 1990. Diagnosing obesity as a high BMI centile (such as the 98th centile or above on the UK charts) identifies …

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