AN international research study led by Southampton University has found that obese patients who undergo surgery to lose weight are not at increased risk of broken bones in the first few years after the operation.

But there is a possible increased risk of fracture after three to five years.

Their report, published in the British Medical Journal, compared people who had undergone bariatric surgery between 1987 and 2010 with a matched group who had not had surgery.

Weight loss, or bariatric surgery, is increasingly used to treat people with life-threatening obesity that do not respond to non-surgical treatments.

The most widely-used forms are gastric by-pass and gastric band.

A band is used to reduce the size of the stomach so people feel full more quickly, while a by-pass re-routes the digestive system past most of the stomach so less food can be digested.

In the UK, patients cannot have the operation performed on the NHS unless they have a body mass index of 40 or above, or 35 with a serious health condition that could be improved by weight loss, such as high blood pressure or type two diabetes.

Surgery is not an easy option.

The risk of dying shortly after bariatric surgery is relatively high at one in 200, but in patients with additional problems such as a BMI of 50 or above or high blood pressure, the risk can be as high as one in 40.

Patients have to commit to a lifelong eating and exercise plan to avoid long-term health complications or regaining weight.

Previous studies have also suggested that bone density is lost after bariatric surgery, which could potentially lead to osteoporosis and an increased risk of broken bones.

But Dr Nicholas Harvey, senior lecturer at Southampton’s Medical Research Council Lifecourse Epidemiology Unit, said: “It has been recognised that surgical treatment is the most effective route to weight loss for many with morbid obesity.”

Cyrus Cooper director and professor of rheumatology at the MRC LEU, said: “With increasing numbers of obese individuals in the UK, bariatric surgery is becoming more common and has been associated with a reduction in bone density after the operation.

“This is the first time that we have been able to investigate risk of fracture following bariatric surgery by comparing patients with non-surgical controls. The results suggest that, at least in the short term, such changes in bone density are unlikely to lead to increased fracture risk.”

Among those who have admitted to having the procedure are former Daily Echo Bournemouth reporter Anne Diamond, TV presenter Fern Britton and former X Factor judge Sharon Osbourne.