One in five reception-year children in Northampstonshire is overweight, rising to one in three by the age of 11, according to new figures from Public Health England.
The organisation says it's concerned at the amount of sugar being eaten by children, especially at breakfast time.
Orla Hugeniot, senior campaign nutritionist at Public Health England, said children were having "too much sugar".
She said: "Children are having roughly around 11g of sugar at breakfast time alone.
"That's almost three cubes before they start the day".
Last year it was revealed that children as young as two were going into hospital and having all of their teeth removed because of decay.
The recommended daily maximum is no more than five cubes of sugar for four- to six-year-olds and no more than six cubes for seven- to 10-year-olds per day.