Overweight children have an increased chance of becoming overweight adults. Increased weight in adulthood can lead to long-term conditions such as Type 2 diabetes. There are some simple tips you can use to help your child regain a healthy weight. Checking what their BMI is can help too.
https://www.nhs.uk/live-well/healthy-weight/childrens-weight/advice-for-parents-overweight-children/