There has been a four-fold increase in the number of children admitted to hospital for problems related to obesity in England and Wales between 2000 and 2009.

According to research conducted by Imperial College London, nearly three quarters of the admissions were to deal with problems complicated by obesity such as asthma, breathing difficulties during sleep, and complications of pregnancy, rather than obesity itself being the primary reason.

In 2009 there were 3,806 children admitted to hospital for obesity-related conditions - compared with a mere 872 in 2000.

Imperial College's Dr Sonia Saxena, who led the study, said: "The burden of obesity is usually thought to have its serious consequences in adulthood, but we now see it manifesting earlier, in childhood.

"It's clear that rising obesity levels are causing more medical problems in children, but the rise we observed probably also reflects increasing awareness among clinicians, who have become better at recognising obesity."

National surveys in England suggest that around 30 per cent of children aged two to 15 are overweight and 14 to 20 per cent are obese. Children who are obese have a higher risk of health problems such as type 2 diabetes, asthma, and sleep apnoea.

The findings are published in the open access journal Plos One.