The number of children with the type of diabetes which is linked to being obese is much higher than first thought, according to recent figures.
Experts had thought there were only 100 under 16-year-olds in the UK with type 2 diabetes, normally found in adults.
But recent a study in east London found 22 children with the disease living in that area alone.
This type of diabetes was very rare in children, but it's now thought up to 1,500 children in the UK could have it.
The leap in the number of children who are obese could be to blame for the increase.
Healthy diet's important
Douglas Smallwood, head of the charity Diabetes UK said: "Unless children are educated to eat a healthy diet and take up physical activity the number of children with the condition will continue to increase."
The body uses a special hormone called insulin to convert food we eat into a kind of sugar called glucose, and glucose then gives us energy.
People with type 2 diabetes don't make any or enough insulin, or can't use it properly in their body.