One million obese children under 16 live in the UK - a third of the total in Europe - according to a report from Britain's doctors which urges the government to intervene in schools, to improve the nation's diet and exercise habits.

The cost of childhood obesity is soaring. Doctors from the British Medical Association said yesterday that children and young adults were now arriving in their surgeries with the diseases of late middle-age.

At the launch of the BMA's report, called Preventing Childhood Obesity, Sam Everington, a GP at the Bromley by Bow health centre in London, said he now regularly tests children for type 2 diabetes, which is associated with obesity and used to be seen only in adults. "There's now a new disease, called diabesity," he said.

Dr Everington said he had started to measure children's blood pressure and cholesterol levels, which would once have been unheard of. "The situation is much worse than people think," he said. "A quarter of the children I see are overweight and blood tests show that more than 50% are malnourished." Typically they had iron deficiency and low levels of vitamins and minerals in their blood because of their poor diet.

He also saw children suffering from sleep apnoea, in which their weight gives them problems breathing in the night, and bone disease.

The BMA is calling for the government to mount a sustained and consistent public education campaign for parents and children on the benefits of a healthy lifestyle.

"It is madness that at a time when children are being told to eat less and do more exercise, they go into school and are sold fizzy drinks and doughnuts and do less than two hours timetabled exercise a week," said Vivienne Nathanson, head of science and ethics at the BMA.