The National Child Measurement Programme (NCMP) has been running since the school year 2006/07. Virtually all children in reception year (Year R) aged 4-5 years of age and all children in the last year of primary school (in Year 6) aged 10-11 years have their height and weight measured generally by school nurses coming into the schools, although measurements were incomplete for some local authorities for 2019/20 due to the COVID-19 pandemic (all schools in Hull had completed the measurement prior to the school closures in March 2020 so it did not affect Hull) and for 2020/21.
The body mass index (BMI) is used for children, but given that children of different ages and genders grow and develop at different rates, the method used to define weight classification in UK children differs to the methods used for adults.
Among children, the cut-off values to define overweight and obesity differ depending on the age and gender of the child. The cut-off values are based on 1990 reference curves and defined on the basis of centiles. Underweight was defined as a BMI less than or equal to the second centile, healthy weight as a BMI above the second centile but less than the 85th centile, overweight as a BMI the 85th centile or above but less than the 95th centile, and obese as a BMI the 95th centile or higher. Thus in 1990, 2% of all children were defined as underweight, 15% as overweight and 5% as obese.
Cole, T.J., J.V. Freeman, and M.A. Preece, Body mass index reference curves for the UK 1990. Archives of Diseases in Childhood, 1995. 73: p. 25-29.
NHS Digital. National Child Measurement Programme. https://digital.nhs.uk/services/national-child-measurement-programme
National Obesity Observatory. A simple guide to classifying body mass index in children, June 2011.
Also see Body Mass Index.