More than a third of children in England are overweight/obese, according to a 20-year study of electronic health records, published online in Archives of Disease in Childhood.

But the rapid rise in prevalence may be starting to level off—at least in younger children—the findings indicated, although there are no grounds for complacency, researchers warned.

They scrutinized the anonymized electronic healthcare records of more than 370,500 children, aged 2 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 researchers wanted to track any changes in the prevalence of overweight and obesity over these two decades.

The children were patients at 375 general practices across England. Their anonymized health data had been entered into the U.K. Clinical Practice Research Datalink, a large database containing the health records of around 5.5 million patients registered with 680 general practices around the U.K.

The analysis showed that between 1994 and 2003 the prevalence of 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 that it may have leveled off, researchers said.

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

Among the boys, the prevalence of overweight/obesity among 2-5 year olds ranged from around one in five (19.5%) in 1995 to one in four (26%) in 2007. Among 6-10 year olds, prevalence ranged from 22.6% in 1994 to 33% in 2011.

The highest figures were seen in 11-15 year olds, among whom the prevalence of overweight/obesity 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 6-10 year olds.

Once again, the highest rates were among 11-15 year olds, ranging from 28.3% in 1995 to 36.7% in 2004 and 2012.

Overall, the increase in rates of overweight/obesity was significant for all age groups in the first decade of the study, but it was only significant in the second decade for 11-15 year olds.

Rates among this age group continued to rise in the second decade, albeit more slowly than in the first.

“There are several possible theories for the recent stabilization of childhood overweight and obesity rates,” the researchers wrote. “One explanation may be that rates have reached a point of saturation.” Alternatively, public health campaigns may actually be starting to work, they said.

In a linked editorial, Professor Julian Hamilton-Shield and Dr. Debbie Sharpe, of the University of Bristol, pointed out that the implications for such levels of teen obesity are “profound” in terms of current and future health.

They went on to say that many of the techniques used by local authorities in England, who have assumed responsibility for obesity as part of their public health remit, are not based on strong evidence, and there is little in the way of outcomes data to determine how successful they are.

Furthermore, many parents and clinicians remain to be convinced that childhood obesity is a serious enough health concern, they said, suggesting that it may be time to revisit the idea of implementing a “fat tax.”

“Thus far, we simply do not seem to have the tools to manage this problem effectively,” the editorialists wrote. “The childhood obesity crisis in England is far from over, and our current weapons in the war against fat seem unlikely to provide the answer.”

They added: “The recent call to the chief medical officer to develop a ‘child obesity action group’ may prove a first step in what is likely to be a very long campaign.”