The number of 10 and 11-year-olds classed as severely obese in the final year of primary school is nearly double that of those in reception, new analysis has found.
Figures show more than 22,000 (4.1 per cent) out of 556,000 of children in Year 6 were classed as severely obese in 2016/17.
The LGA, which represents 370 councils in England and Wales, warned the severe child obesity rates are contributing to a "multi-billion pound ill-health time bomb".
Severe obesity puts people at serious health risks, including 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 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.
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.
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Despite budget reductions, it said councils are spending more on running effective prevention schemes to help children stay healthy, which is key to tackling the child obesity crisis and reducing future costs to hospital, health and social care services.
But it added that this prevention work, including the ability of councils to provide weight management services for children and adults, is being hampered by a £600 million reduction in councils' public health budgets by central government between 2015/16 and 2019/20.
The LGA is calling for the budget cuts to be reversed.
Tam Fry of the National Obesity Forum said the obesity crisis could take ten years to solve, and more physical activity in schools was the answer.
"Some parents now are living in an environment that doesn’t make it easy for them to raise children," he said.
"They’ve got little money, little good food, and they have to survive on food that’s processed or full of fats and sugar. Unless the children are advised to burn all that off it’ll stay with them, that’s why those early years are so crucial."
"Theresa May has said all schools should offer half an hour of physical activity to all their children in primary school, that should be extended to after school where after school clubs could allow the children to have one hour of activity they need every day," he added.
"[Schools] need to teach children how to grow up properly and become the parents of the future. It’s going to take a another ten years to get this obesity problem sorted."
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."