Surgical answer to obesity

MEDICAL MATTERS: Anne Diamond, the TV presenter who has publicly battled a weight problem, was recently criticised after she admitted having obesity surgery before appearing on the reality TV show, Celebrity Fit Club. She was accused of using the surgery as an additional slimming aid for the series, an allegation she robustly denied.

Ms Diamond is just one of a number of people who have turned to surgery as the answer to a chronic weight problem. In Italy, the number of weight-loss procedures has doubled in the past three years. And in the US, the number of people undergoing a stomach bypass for obesity more than tripled between 1995 and 2000.

Despite the increase in the number of procedures being undertaken, surgery is not an option for everyone who is overweight. At present, doctors here, in Britain and in the US restrict obesity surgery to the so-called morbidly obese - people whose body mass index (BMI) is greater than 40 kg/m2. (To calculate your BMI, divide your weight in kilograms by your height in metres squared). Patients with a BMI greater than 35 and who have other medical conditions made worse by obesity are also eligible for surgery. In addition, candidates for surgery are psychologically assessed.

The most popular type of gastric bypass procedure performed in these islands and the US is called a Roux-en-Y-gastric bypass (RNYGB) after the French surgeon who developed the technique. Using keyhole surgery, the top of the stomach is divided off and lined with staples to create a small pouch. A new exit from this smaller stomach is connected into the far end of the small intestine, so that the remainder of the stomach and a segment of the intestine is bypassed, creating a new Y-shaped structure. The length of the intestine is carefully calculated to ensure the patient will be able to eat enough to maintain a normal weight.

The procedure induces weight loss in two ways: the capacity of the stomach is much reduced and the loss of the small intestine means that the absorption of food is restricted. Research has shown that people who have had the RNYGB lose 50-75 per cent of their excess weight in the two years after surgery. This technique produces the most significant and sustained weight loss.

Gastric bands, the type of surgery chosen by Ms Diamond, have been in use since the mid- 1980s. The surgery is formally called a laparoscopic adjustable gastric band (Lap-band) procedure and is carried out with a flexible telescope using a series of small incisions across the upper abdomen. The band is placed around the upper stomach and locked in place. It has an inner balloon which is connected by tubing to a reservoir of fluid. By increasing the amount of fluid in the balloon, it inflates and makes the band tighter so that the opening between the small pouch created by the band and the rest of the stomach can be adjusted. Weight loss is achieved by restricting the volume of food the patient can take in; they must adjust to eating slowly and chewing well. Patients lose 52-65 per cent of their excess weight following gastric banding.

A gastric balloon is a temporary weight-loss option. The procedure involves placing a silicone balloon in the patient's stomach via the throat, using a flexible scope. The balloon is then filled with saline. It can be left there for a maximum of six months; otherwise the risk of deflation and intestinal obstruction become too great. However, although the balloon does produce weight loss, the tendency is for patients to regain weight once it has been removed.

What about the risks and side effects of obesity surgery? The death rate from gastric banding and RNYGB is 0.25-0.5 per cent. This is most commonly due to a combination of deep vein thrombosis and a blood clot to the lungs. The staple line in the stomach bypass procedure can break down, leading to a leak of gastric fluid. And a gastric band may slip or even erode into the stomach wall. Patients must be followed up for life to ensure they do not develop any metabolic problems as a result of malabsorption. There is a particular risk of iron and B12 deficiency with the RNYGB; vitamin D and calcium absorption may also be affected.

But when it works, the benefits of surgery are striking. Up to 60 per cent of people who had obesity-related illnesses such as diabetes, high blood pressure and sleep apnoea no longer need medication for them three years after the operation. Obesity surgery is not for everyone; fewer than 100 procedures have been carried out in the public health system here. But for those whose lives are at risk from severe obesity, surgery has a definite role to play.

Dr Muiris Houston is pleased to hear from readers but regrets that he cannot answer individual queries.