Most 10-year-olds have eaten at least 138kg (304lb) of sugar by the time they reach adulthood, according to Public Health England (PHE).
The data - gathered from household eating habits across the UK - comes as the government agency launches a campaign encouraging parents to reduce the amount of sugar their children eat.
It is recommended that the maximum amount of sugar for 10-year-olds is 20 to 24g a day - the equivalent of five sugar cubes.
However, a PHE survey has found that children are consuming an average of 52.2g a day, eight more cubes than the recommended level.
PHE's Change4Life campaign is encouraging parents to change their shopping habits by switching the brands of yoghurts, drinks and cereals they buy - a move which could cut a child's sugar intake by half.
Over the course of a year, opting for healthier products could remove the equivalent of 2,500 sugar cubes from a child's diet.
The campaign comes as severe obesity in children aged 10 and 11 hits an all-time high.
A third of youngsters leave primary school overweight or obese and more young people than ever are developing Type 2 diabetes.
PHE says overweight children are more likely to remain that way when they grow up and are at a greater risk of heart disease and some cancers.
Alison Tedstone, PHE chief nutritionist, said: "Children are consuming too much sugar, but parents can take action now to prevent this building up over the years.
"To make this easier for busy families, Change4Life is offering a straightforward solution - by making simple swaps each day, children can have healthier versions of everyday foods and drinks, while significantly reducing their sugar intake."
Parents can download an app which makes it easier to identify low-sugar options, and look for products that display the Change4Life Good Choice badge in shops.