Increasing numbers of boys and girls under the age of 11 are now obese, official figures for England show.
Obesity levels were higher in deprived areas
Between 1995 and 2003, the prevalence of obesity among children aged two to 10 rose from 9.9% to 13.7%, the Department of Health found.
The biggest increase seen in an age group was among eight to 10 year-olds, from 11.2% to 16.5% over the eight-year period.
Obesity experts said the statistics were alarming.
Obesity also rose significantly in the poorest areas of the country.
Levels of obesity were five percentage points higher among children living in the most deprived areas than the least deprived areas of England.
Obesity levels were lowest in Yorkshire and the Humber and the South East (11-13%), and highest in the North East and London (about 18%) in 2001/2.
Children living in inner city areas were particularly prone to obesity.
The number of children who were overweight, and possibly on the road to full-blown obesity, had also risen.
More food, less exercise
Children of parents who were themselves obese were much more likely to be overweight.
About 20% of children living in a household where both parents were overweight or obese were themselves obese compared with 6.7% of children living in households where neither parents were overweight or obese and 8.4% of children where one of the two parents were overweight or obese.
Dr Ian Campbell of the National Obesity Forum said: "These statistics are very worrying indeed.
"Clearly we are in the middle of an epidemic that is wreaking havoc on our children."
He said it was down to children consuming more calories and being less active than they ought to be.
"It's the fact that calories have become cheaper and exercise expensive."
"It's a travesty that this country, which has got a wealth of resources, has been neglecting the welfare of our children in this way."
But he said we should be able to tackle this problem as a nation because we had the expertise and the will in government to do it.
"Now is the time to stop it. The optimal time to intervene is in childhood, before irreversible damage has been done and while lifelong good habits can be learnt."