A group of Cambridge scientists have shown that obesity can result from a genetic defect, rather than over eating.

Led by Dr Sadaf Farooqi of the University of Cambridge and Dr Matt Hurles from the Wellcome Sanger Institute just outside Cambridge, the scientists studied 300 children with severe obesity.

The team scanned each child’s entire genome looking for “copy number variants” – large chunks of DNA which have been duplicated or deleted from our genes – and found that certain parts of the genome were missing in some severely obese patients.

Dr Matt Hurles said: “This is the first evidence that copy number variants have been linked to a metabolic condition such as obesity”.

The study has implications for social workers, who for years have put overweight children on the “at risk” register in the belief that they are being over fed by parents.

Some of the children involved in the study were on the “at risk” registers when the tests began, but have since been removed.

“This study shows that severe obesity is a serious medical issue that deserves scientific investigation” said Dr Farooqi, “It adds to the growing weight of evidence that a wide range of genetic variants can produce a strong drive to eat.”

Obesity is widely recognised as one of the UK’s chief public health concerns, nearly a quarter of British children are classed as clinically obese.