More than a third of children in England are overweight or obese, according to a 20-year study of electronic health records.
However, a rapid rise in the problem may be starting to level off, at least in younger children, the findings indicate, though the researchers warned there are no grounds for complacency.
They looked at the anonymised 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 (1993 to 2013).
The children were patients at 375 general practices across England, whose data was in the UK Clinical Practice Research Datalink, a database containing the health records of around 5.5 million patients registered with 680 general practices.
The analysis showed that between 1994 and 2003 the prevalence of being overweight and obesity in all children increased by just over 8% each year.
But the rate slowed substantially between 2004 and 2013 to 0.4% 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 (19.5%) in 1995 to one in four (26%) in 2007.
Among six to 10-year-olds, the rate ranged from 22.6% in 1994 to 33% 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 (26.7%) in 1996 to almost four out of 10 (37.8%) in 2013.
These patterns were similar among girls. The prevalence ranged from 18.3% in 1995 to 24.4% in 2008 among the youngest, and from 22.5% in 1996 to 32.2% in 2005 among six to 10-year-olds.
Once again, the highest rates were among 11 to 15-year-olds, ranging from 28.3% in 1995 to 36.7% in 2004 and 2012.
"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.
The findings are published online in Archives of Disease in Childhood, one of more than 50 specialist journals published by BMJ.
The campaigns manager of British Cycling, Martin Key, said: "Obesity levels in children under 10 may be levelling off, but the fact remains that one third of kids in England are overweight or obese.
"Building physical activity back into our children's lives would go a long way to tackling this problem.
"Less than 2% of children cycle to school compared with the Netherlands, where half of all kids cycle to school and obesity rates are significantly lower.
"A focus on building accessible and segregated cycle lanes near major school routes would provide the incentive for parents to ditch the car and inspire their children to be more active."