More than a third of children in England are overweight or obese, according to a 20-year study of electronic health records - but the rapid rise may be starting to level off.

Researchers looked at the anonymous electronic health care records of more than 370,500 children, aged two to 15, who had accumulated more than half a million weight (BMI/body mass index) assessments between them over a period of 20 years from 1993 to 2013.

The children were patients at 375 general practices across England.

The analysis showed that between 1994 and 2003 the prevalence of being overweight and obesity in all children increased by just over 8 per cent each year.

But the rate slowed substantially between 2004 and 2013 to 0.4 per cent a year, suggesting it may have levelled off.

Trends were similar for both boys and girls, but differed by age group.

Among the boys, the prevalence of being overweight or obese among two to five-year-olds ranged from around one in five in 1995 to one in four in 2007.

Among six to 10-year-olds, the rate ranged from 22.6 per cent in 1994 to 33 per cent in 2011.

The highest figures were seen in 11 to 15-year-olds, among whom the prevalence of being overweight or obese ranged from around one in four in 1996 to almost four out of 10 in 2013.

These patterns were similar among girls. The prevalence ranged from 18.3 per cent in 1995 to 24.4 per cent in 2008 among the youngest, and from 22.5 per cent in 1996 to 32.2 per cent in 2005 among six to 10-year-olds.

'There are several possible theories for the recent stabilisation of childhood overweight and obesity rates,' write the researchers, led by Dr Cornelia van Jaarsveld, of the Department of Primary Care and Public Health Sciences, King's College London. 'One explanation may be that rates have reached a point of saturation.'

Alternatively, public health campaigns may actually be starting to work, they say.