But parents shouldn’t expect surgery to be a quick fix for clinically obese teens.

Scientists at Monash University and the Royal Children’s Hospital in Melbourne studied 50 teenagers over two years.

Half the teens were placed in a highly supervised program that involved diet plans, exercise and behavioural changes.

The other half had lap band surgery, an operation that places a band around the stomach, making it much smaller and reducing appetite.

The 25 teens in the lifestyle program lost an average of 3kg per person – or 13 per cent of their excess weight - while the teenagers who had surgery lost an average of 35kg, or 79 per cent of their extra weight.

Professor Susan Sawyer, director of the hospital’s Centre for Adolescent Health, said that the study showed lap band surgery could be an effective treatment for a small number of teenagers with extreme obesity that was affecting their health.

But she said Australia needed more publicly funded programs to treat children with severe obesity, using methods that included lifestyle changes, medication and behaviour changes as well as surgery.

“Lapbanding might be just one arm of that because clearly this is not our first point of call it is our last point of call,’’ she said.

The study is published in the Journal of the American Medical Association.