There was a steady rise in the proportion of overweight children between 1994 and 2003, but in the past decade it has remained at about 30%.

The King's College London researchers add obesity rates among 11- to 15-year-olds are still rising, however.

And Public Health England said there was no room for complacency.

Experts believe that being significantly overweight is responsible for a wide range of health problems such as heart disease, type 2 diabetes, some cancers and infertility.

The number of obese people in the UK has more than trebled in the past 25 years.

Obesity levels among children have also been rising during this period. One in three children in the UK is now overweight, while one in five is obese.

But data from other sources had previously suggested that childhood obesity levels were now starting to plateau or even fall slightly.

Age-group trends

This study, published in the Archives of Disease in Childhood, used GPs' electronic health records in England to monitor trends over 20 years.

Weight, height and body mass index (BMI) measurements for more than 370,000 children from 1994 to 2013 were analysed.

The findings show that the rate of growth of overweight and obesity levels, which was 8% each year up to 2003, has slowed substantially in the past 10 years, to 0.4%.

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

Overweight and obesity levels among two- to five-year-olds stayed relatively stable at 25% for boys and 23% for girls between 2003 and 2013.

In six- to 10-year-old girls and boys, about 30% were overweight or obese during that time.

The highest figures were seen in 11- to 15-year-olds, where overweight and obesity levels ranged from about 26% in 1996 to 35% in 2003.

Among this group, overweight and obesity levels have continued to rise - to 37% - in the past decade. 

The study defined overweight as equivalent to a BMI (body mass index) at or above the 85th centile and obesity as above the 95th centile.

'Vulnerable group'

Dr Cornelia van Jaarsveld, from the department of primary care and public health sciences at King's College London, said there were several possible reasons for the "recent stabilisation of childhood overweight and obesity rates".

She said public health campaigns and initiatives could be starting to work.

But another explanation could be that a ceiling or "saturation point" had been reached with obesity rates.

However, she said it was clear that the 11- to 15-year-olds were still a "vulnerable and difficult group".

Colin Michie, chair of the nutrition committee at the Royal College of Paediatrics and Child Health, said the good news was that things were not getting worse.

"But it still leaves us with lots of problems, particularly among teenagers, who are not easily directed, at a sensitive time in their lives," he said.

"It is a disappointment that even more children are overweight and obese at the end of primary school than at the beginning.

"Prevention works better in younger age groups, so we have to focus on cutting calories and encouraging a more active, healthy lifestyle in children."

Eustace de Sousa, national lead for children, young people and families at Public Health England, said that overall childhood obesity rates had remained stable since 2010.

"However for children from the poorest households levels have continued to worsen, so there is no room for complacency.

"Obese children are more likely to experience bullying, low self-esteem, anxiety, depression and have a higher risk of developing type 2 diabetes and heart disease in later life."

Source: BBC