Health experts have warned of obesity’s “overwhelming” burden on the NHS as figures showed a 785% rise in weight-loss surgery.

Some doctors are “skirting around the rules” and not insisting on months of lifestyle change and pharmaceutical treatment before allowing patients to undergo surgery, specialists said.

Operations carried out for the most obese people in England soared over the past five years, according to the NHS Information Centre.

Data for 2003/04 showed there were 480 procedures, rising to 4,246 in 2008/09.

Tam Fry, from the National Obesity Forum, said: “These figures just show how bad things have got with the obesity epidemic.

“We have alternative ways of losing weight but when people realise this is a possibility, they could go for it.

“A lot of doctors are also starting to skirt around the rules and not insist on months of lifestyle change and pharmaceutical treatment - instead they are going straight for surgery.”

Peter Sedman, bariatric surgeon and spokesman for the Royal College of Surgeons, said: “The number of morbidly obese patients in the UK is increasing rapidly and we need to continue to put even more resources into what is proven to be a successful and cost-effective method of treatment.

“The burden on the NHS in years to come in obesity-related illness will otherwise be overwhelming.”

The upward trend of operations suggests figures for 2010 could be even higher.

From 2003/04 to 2004/05, the number of procedures jumped from 480 to 747.

It then rose again the following year to 1,023, then 1,928 in 2006/07, 2,703 in 2007/08 and 4,246 in 2008/09.

Health minister Paul Burstow said: “Our ambition is to encourage healthier lifestyles and reduce the need for this type of treatment.

“Our public health white paper later this year will set our plans to help people lead healthier lifestyles in more detail.”

A Department of Health spokesman said prescribing drugs or recommending surgery was a “clinical decision”.

“It is up to individual trusts to commission a range of services to meet their local community’s needs.”