Obesity surgery poses a classic medical dilemma: do you provide the operations and risk sending a message that obesity is a "curable" condition, or restrict them and deny a proven treatment to the seriously ill?

Gross obesity is a medical emergency. If you are so fat you cannot get up the stairs, or walk more than a few yards without getting out of breath, any minor medical problem can become life threatening. In those circumstances, surgery can be lifesaving. Its effects are often dramatic, with patients losing many stones in weight in months.

But if any surgery deserves the term "heroic", this is it. It is expensive to carry out, high-risk (with a 14 per cent complication rate) and one in 200 patients die.

The effects are lifelong, requiring a permanent change in the diet and are psychological as well as physical. Adjusting to a new shape and dealing with a partner who may still be obese present challenges. Further surgery may be required to remove excess skin folds as weight is lost or to adjust a gastric band – one in five bariatric operations is for "maintenance".

It is not, in other words, for the faint-hearted. Yet it pays for itself in improved health and reduced treatment costs and other benefits within a year.

The NHS may struggle to find the cash to pay for it – but the cost of not doing so will be even higher.