Figures revealed that 183 youngsters under 11 in England, Scotland and Wales have been recorded as weighing more than 16st in the last three years.
Eight were more than 20st and the heaviest weighed 23st 2lb.
There has been a 12% rise in the number of under-16s admitted to hospital for obesity in the last year, figures released by the Health and Social Care Information Centre (HSCIC) this week show.
Across all ages, obesity admissions across England were lower for every age group except the under-16s and those 65 and over.
Using Freedom of Information laws, the newspaper approached the 206 local authorities in Britain with responsibility for child protection.
Of the 128 councils that provided usable responses it was found that between 26 and 46 morbidly obese children were taken by social services; when taking the potential figure from the remaining councils, the figure could be as many as 74.
Social services removed the children from their families for their protection because their excessive weight caused major health concerns.
Nottinghamshire County Council had seven children taken into care, the highest number of those councils that responded. Oxfordshire saw three children under 16 removed from their parents by social services, Cornwall and Monmouthshire councils two each, and one child in Havering, Hounslow, Portsmouth, Salford and South Ayrshire.
The two heaviest primary school pupils in England - a boy of 23st 2lb and a girl of 22st 11lb - lived in the North West.
London had 21 of the fattest 100 children in England, followed by the West Midlands with 16 and the South East with 14.
NHS data showed that one in 10 children is obese by the time they start primary school, putting them at risk of developing health problems such as heart disease, type-2 diabetes and cancer.