It is already costing taxpayers and the NHS billions of pounds but it's the explosion in the cases of childhood obesity that is causing alarm, a trebling in the last 20 years and growing.

"Obesity has now been described as the most extraordinary public health problem not only in Britain but in the world, which has been completely ignored by ministries of health and governments" says Professor Philip James, chairman of the International Obesity Taskforce.

Week in Week Out has discovered that while the numbers of people with obesity is rising alarmingly there is a chronic shortage of community dieticians in Wales and its even worse when you look at support for children. Cardiff and the Vale of Glamorgan has only one paediatric dietician for the whole of the area and the waiting list is fifteen months. Many parts of Wales don't even have that. Obesity surgeons are equally scarce.

Across the UK there are only 13 obesity surgeons. Professor John Baxter, Professor of Surgery at University of Wales, Swansea, believes that it's such a big problem there needs to be around 100 specialist surgeons across the country. In Wales he estimates 5,000 people need and actually want surgery to reduce their size, yet he can only perform 20 operations a year and his current waiting list is three years.

"If you're morbidly obese, and you haven't started to suffer yet, you have only a 1 in 7 chance of reaching the normal life expectancy because they die prematurely of strokes and heart attacks" says Professor Baxter.

Week in Week Out gives us a rare insight into the private and painful world of childhood obesity. Cerys is three years old, lives in Barry, and weighs the same as an average ten year old. Already her weight is causing health problems and preventing her from making friends with other children.

Stephanie and Martine are thirteen year olds from Cardiff - both are fourteen stone. On Week in Week Out, they and their mothers talk frankly about how obesity is damaging their lives. Teased about their weight at school and intimidated by the idea of PE, they refuse to go to school.

With little support in Wales, Week in Week Out takes Stephanie and Martine to the only Fat Camp in the UK at the Carnegie Institute in Leeds. There they discover their weight is risking their health but, for the first time, they are given the confidence to change their lives. Stephanie's mother Jakkie Smith calls for urgent action and for similar help to be made available in Wales.

Charlie Fisher is worried that if no help is forthcoming they will end up like him. At 32, he is 24 stone and he has the lifestyle of someone more than twice his age. He has a host of life threatening complaints like diabetes, high blood pressure and heart problems.

Asked about the scarce level of support for people living with obesity in Wales, National Assembly Health Minister Jane Hutt said:

"Obviously I am extremely concerned and I hear situations, not just in terms of people being overweight, but the impact of it, in terms of heart disease etc. We know there are huge problems and of course I'm concerned, and I want to take this forward so maybe your programme can be a launching pad for action in Wales".

A year later, Week In Week Out went back to see how Cerys, Martine and Charlie were doing.