Every year officials measure the height and weight of more than one million children to assess childhood obesity.
Among them was four-year-old Harley from Broughton, a 'fit and sporty'child who was branded overweight, to the anger of his mother Mica.
BMI - body mass index - is measured as a ratio of height to weight.
In adults, the BMI is calculated as their weight in kilograms multiplied by their height in metres squared
For most adults, an ideal BMI is in the 18.5 to 24.9 range.
If your BMI is:
below 18.5 – you're in the underweight range
between 18.5 and 24.9 – you're in the healthy weight range
between 25 and 29.9 – you're in the overweight range
between 30 and 39.9 – you're in the obese range
Children’s BMI is measured differently to adults and age and gender is taken in to consideration.
The Government works out obesity using the 1990 British growth reference chart, a large collection of statistics used to determine a child’s body mass index (BMI).
It defines a child as obese if their BMI is in the charts top five per cent, and overweight if they are in the top 15 per cent.
The data shows that children often develop weight problems while at primary school.
Obesity can lead to a number of health problems later in life including type two 2 diabetes as well as psychological issues such as low self esteem and depression.
In 2017 -18 just 10 per cent of Preston’s children were obese in Reception class.Across England one in five pupils in year six was obese.