The relationship between body mass index and fatness in children varies substantially with age, so a growth reference is used to define overweight and obesity in different age groups. The British 1990 growth reference (UK90) is the most commonly used reference within the UK, and the International Obesity Task Force (IOTF) thresholds, World Health Organization Growth Reference and the Centers for Disease Control (CDC) Growth Reference are more frequently used in other countries.
All estimates in the table below are based on measured height and weight. Children’s BMI is classified as overweight (including obese) where it is greater or equal to the 85th of the UK90 growth reference for population monitoring purposes. Wales and Scotland appear to have a higher prevalence of childhood obesity than England.
Percentage of children obese and overweight (including obese) in the UK and Ireland*
*The Welsh Health Survey stopped collecting the height and weight of children after 2012. Data is now collected through the Child Measurement Programme for Wales for 4–5 year olds.
Note: estimates are based on measured height and weight. Children’s BMI is classified as overweight (including obese) where it is greater or equal to the 85th of the British 1990 (UK90) growth reference.
For more information on the classification of child BMI see our web page on measuring and interpreting BMI in children. And our briefing paper: A simple guide to classifying body mass index in children.
Data for Northern Ireland from the Health Survey Northern Ireland 2014/15 are available here
Trends in England
9.6% of boys and 9.0% of girls in Reception (aged 4-5 years) and 21.7% of boys and 17.9% of girls in Year 6 (aged 10-11 years) are also classified as obese according to the British 1990 population monitoring definition of obesity (≥95th centile) (NCMP 2015/16).
Figure 2 shows the trend in child obesity prevalence using data from the Health Survey for England. A trend of increasing child obesity can be seen between 1995 and 2004. Since then, the proportions of older children who are obese have remained broadly steady. Among younger children, there was a slight dip in the proportion who were obese in 2012, but this has not been sustained.