Childhood obesity levels vary by more than 100 per cent between primary care trusts within London.
A London Health Observatory analysis has found, in addition to huge variations in obesity among schoolchildren across different PCTs, a strong correlation between deprivation and unhealthy weight.
London Health Observatory director Bobbie Jacobson said: “It is a worrying finding that as children grow older, the proportion of obese children becomes a much larger problem than being overweight.
“This is a striking finding for both London’s most deprived and for black communities.”
The report, Weighty Matters, is the first detailed look at national data from the national child measurement programme collected between 2006-08.
The programme is aimed at helping PCTs monitor obesity levels against the national target to reduce, by 2020, the proportion of overweight and obese children to the levels seen in 2000.
The proportion of children at risk of obesity in London is the highest of any strategic health authority region, at 22 per cent compared with an England average of 18 per cent.
Childhood obesity levels among reception year children varied from 6 per cent in Richmond upon Thames, the PCT with the lowest rates, to 14 per cent in Southwark, which had the highest.
Across London, the average figure was 11 per cent.
For Year Six pupils, the figures ranged from 12 per cent to 26 per cent. On average, more than one in five Year Six children were at risk of obesity.
Overall, children from Black African backgrounds were twice as likely to be obese compared with their white British classmates.
Boys are at greater risk of obesity than girls in both years. In reception year the figures are 12 per cent for boys and 10 per cent for girls, with the gap widening by year six to 26 per cent and 12 per cent.