Restrictive bands on the stomach or surgery to bypass part of the digestive tract are sometimes used to help morbidly obese patients lose weight when drugs or changes in diet and exercise fail.

Researchers at the Cleveland Clinic in Cleveland, Ohio, carried out a database trawl to pick out 73 previous studies, covering nearly 20,000 people, that detailed weight and other health issues before and after bariatric surgery.

Three-quarters of the patients were women, whose average age was 41.

After the operation, participants lost on average 54% of the excess weight they were carrying, a tally that ranged from 16 to 87%.

High blood pressure improved in 63% of patients, diabetes in 73% and blood cholesterol in 65% of them.

A further 18 studies, covering 713 other people, found that surgery led to improvements in the heart function, such as its ability to pump out and refill with blood.

The review was not without limitations, the authors said.

The studies did not look at the same operative techniques or share the same criteria for measuring improvements. There were also blanks in “followup,” or monitoring patients for a long time after their operation.

Even so, the picture is strong enough to say that bariatric surgery has gone “beyond the realms of a cosmetic procedure” and to a potentially life-saving option for the right patient, the review said.

It also cautioned of the risks involved in bariatric surgery. Statistics point to a 0.3% risk of death, a five percent risk of intestinal obstruction and 8% risk of an ulcer.