More than a third of all children are either overweight or obese according to Government figures launched this week.
In the figures, a quarter of 11 to 15-year-olds are classified as obese - double the proportion 10 years ago. Among boys the proportion rose from 13.5 per cent to 24.2 per cent and among girls from 15.4 per cent to 26.7 per cent.
When overweight and obesity were taken together, the percentage for girls was 46 and for boys 37 per cent.
Even in children aged two to 10, the proportion of boys classed as obese rose from 9.6 per to 15.9 per cent and in girls from 10.3 per cent to 12.8 per cent.
About 2,000 children aged two to 15 took part in the survey.
Prof Colin Waine, the chairman of the National Obesity Forum, said they revealed a "public health timebomb". Children who are obese aged 11 to 15 are twice as likely to die when they are 50.
"Being obese at adolescence increases the cancer risk by 21 per cent for girls and 14 per cent for boys", he said. "In my youth, playing cricket and tennis was the norm. These have now been replaced by sedentary activities such as watching television and playing video games."