The Local Government Association (LGA), which represents 370 councils in England and Wales, has obtained statistics which it says show children are rapidly gaining weight as they go through school.
And it warns the severe child obesity rates are contributing to a “multi-billion pound ill-health time bomb”.
The first data of its kind for 2016/17, supplied by the National Child Measurement Programme (NCMP), shows a total of 22,646 out of 556,452 (4.1%) of 10 and 11-year-olds in Year 6 are classed as severely obese.
This compares with 14,787 out of 629,359 (2.35%) of four and five-year-olds in reception class.
Severe obesity rates are highest in children living in the most deprived towns and cities, and those from BME groups, which the LGA suggested shows a need for more targeted interventions.
The LGA is calling for reductions in public health grants to be reversed by the government and for further reforms to tackle childhood obesity.
This includes councils having a say in how and where the soft drinks levy is spent, better labelling on food and drink products, and for councils to be given powers to ban junk food advertising near schools.
Councillor Izzi Seccombe, chairwoman of the LGA’s Community Wellbeing Board, said: “These new figures on severely obese children, who are in the most critical overweight category, are a further worrying wake-up call for urgent joined-up action.
“The UK is already the most obese nation in western Europe, with one in three 10 and 11-year-olds and one in five four and five-year-olds classed as overweight or obese, respectively.
“Unless we tackle this obesity crisis, today’s obese children will become tomorrow’s obese adults whose years of healthy life will be shortened by a whole host of health problems including diabetes, cancer and heart disease.”
Ms Seccombe says cuts to councils’ public health grants are having a significant impact on early intervention services.
People who are severely obese have a higher risk of diabetes, heart disease, stroke and cancer.
Severe obesity can also shorten a person’s life by 10 years – an equivalent loss to the effects of lifelong smoking.
In adults, a body mass index (BMI) of 40 or above means a person is severely obese, at least 60% higher than the upper healthy weight BMI limit of 24.9.
BMI takes into account natural variations in body shape, giving a healthy weight range for a particular height.
It is calculated by dividing weight in kilograms by height in metres squared.
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A Department of Health and Social Care spokesman said: “Our childhood obesity plan is among the most comprehensive in the world – our sugar tax is funding school sports programmes and nutritious breakfasts for the poorest children, and we’re investing in further research into the links between obesity and inequality.
“However, we have always been very clear that this is the not the final word on obesity, and we have not ruled out further action if the right results are not seen.”