More than a third of children leaving primary school in Leeds are overweight or obese, according to new figures.
In total just over a third (34.9 per cent) of 10 and 11-year-olds in the city are too heavy.
And one in five year six pupils in Leeds is obese and levels of obesity double between youngsters starting school and leaving aged 10 or 11, the statistics show.
But there has been a slight decrease in the proportion of the city's children who are dangerously heavy.
Being overweight or obese can lead to serious health problems, including diabetes, heart disease and cancer.
Latest figures from the Government's National Child Measurement Programme show 10.1 per cent of children in reception classes and 20
per cent of year six youngsters in Leeds are obese.
Among four and five-year-olds in the city, 13.6 per cent are overweight, while 14.9 per cent of 10 and 11-year-olds are.
An NHS Leeds spokesman said: "We recognise that there is a lot more to do if we are to significantly reduce childhood obesity in Leeds.
"We are confident that by working with our partners across the city we can tackle the issue and prevent children in our city developing health problems in future linked to obesity."
He said initiatives included supporting the national Change 4 Life anti-obesity campaign, training children's centre staff on the award-winning HENRY (Health, Exercise and Nutrition for the Really Young) programme, running physical activity projects and encouraging schools to achieve the national Healthy Schools status.
In Wakefield, there has been a rise in levels of childhood obesity to 10.1 per cent of reception class pupils and 19.5 per cent of older children.
Nationally almost 10 per cent of children in the first year of school are obese and 18.7 per cent of those leaving primary school are.