Nearly one in five children in England leave primary school obese, figures show.
The data, from the school measuring programme, also showed one in 10 pupils start school obese.
The figures show small rises from previous years although as the scheme is voluntary it is hard to draw firm conclusions.
Predictions from a separate report last year suggested childhood obesity was levelling off.
More than 1m children took part in the measuring scheme
In total, 18.7% of year six pupils were obese, the report released by the NHS Information Centre showed. The figure rises to 33.4% when overweight children are taken into account.
For the reception year, the figures are 9.8% and 23.1% respectively.
All these measures show slight increases from 2008-9, although the NHS Information Centre which produced the report said they were not statistically significant.
This is mainly because parents can refuse to let their children take part in the programme - and one in 10 do.
Nonetheless, more than 1m children took part, making it the largest child weight survey of its kind.
Tim Straughan, chief executive of the NHS Information Centre, said: "These statistics suggest that more needs to be done at a younger age to combat obesity within primary education and positively encourage healthy eating and participation in physical activity to reduce future health implications for these children."
Tam Fry, from the National Obesity Forum, said the figures were shaming.
"The fact that obesity doubles during the primary school years from reception year shows that the government must rethink its recent proposals on school dinners and physical activity."
Dr Helen Walters, obesity spokesperson for the UK Faculty of Public Health, said she still believed the rise in obesity was beginning to tail off.
Bue she added: "The situation will take decades to sort out and as it stands, the picture remains bleak."