More than 2,100 children, less than 16 years, were treated for eating disorders in the last three years, finds a study.
While 600 children were below the age of 13, 197 children were between the ages of five and nine - with cases within this age group almost doubling over the period, reports the Telegraph.
Almost 400 were between the ages of 10 and 12, while more than 1,500 were aged 13 to 15.
Even these statistics, disclosed under the Freedom of Information Act, are likely to be an underestimate, the research said.
Susan Ringwood, chief executive of eating disorders charity B-eat said the figures reflected alarming trends in society, with young children "internalising" messages from celebrity magazines, which idealised the thinnest figures.
"A number of factors combine to trigger eating disorders; biology and genetics play a large part in their development, but so do cultural pressures, and body image seems to be influencing younger children much more over the past decade," she added.
The study has been published in the British Journal of Psychiatry.