The European study found the UK has the second highest proportion of overweight children out of the 28 countries that were able to provide data.
With 23.1 per cent of youngsters in the age group classed as overweight or obese, the UK was second only to Ireland at 27.5 per cent.
They were followed by Albania, Georgia, Bulgaria and Spain.
Kazahkstan had the lowest obesity rate, with other low prevalence nations including Czech Republic, Belgium and Sweden.
Another study, which is also being presented at the European Congress on Obesity in Prague this week, found that children as young as six are suffering dissatisfaction with their bodies.
The research, carried out by Leeds Beckett University, found that children who were classed as overweight or obese on body mass index (BMI) growth charts had higher body shape dissatisfaction scores than normal-weight children.
Girls also had higher scores than boys.
Overweight and obese pupils reported more dietary restraint than their normal-weight peers, which researchers said might lead to them compromising the quality of the diet at a time when they need a good quality, healthy diet for growth and development.
Lead researcher Professor Pinki Sahota said: “The results suggested that body shape dissatisfaction and dietary restraint behaviours may begin in children as young as six to seven years old, and there is an association with increased BMI.
“Obesity prevention programmes need to consider psychological well-being and ensure that it is not compromised. Further research should be conducted on how interventions can help improve psychological well-being in this age group.”