There's been a lot of fuss surrounding Fern Britton and her gastric band, but what exactly is the procedure and how does it work?

During gastric banding an adjustable, silicone band is placed around the upper part of your stomach to create a small pouch. This pouch quickly fills up when you start eating, so you feel full and can only eat small meals. The operation involves a general anaesthetic and, if possible, the band is fitted using keyhole (laparoscopic) surgery rather than an open operation.

The band contains a fluid-filled balloon that can be tightened or loosened by adjusting the amount of fluid it contains. Fluid is added or removed via a tube that runs to a reservoir implanted under the skin below your rib cage. Saline is added or removed from the band using a special needle inserted into the reservoir. The tightness of the band is adjusted after swelling settles down a couple of weeks after the operation, and whenever necessary to balance the amount you can eat against optimal weight loss.

The procedure does not involve cutting or removing any part of the stomach, making it safer than some other procedures, such as gastroplasty, where the stomach is stapled to make it smaller, or a by-pass, where the stomach is made smaller and food is sent on a different route through the intestines so less is absorbed.

As with all surgery however, there is a risk of side effects with gastric banding, especially as those involved are obese, which makes any operation more risky. Potential complications include those of general anaesthesia (eg aspiration pneumonia) and of surgery (eg haemorrhage, wound infection, deep vein clots, intestinal puncture).

The band itself can also cause problems such as making you feel nauseated or being sick after eating. One in ten people need further surgery because the band has slipped, leaked, become infected, eroded through the stomach wall or needs to be removed due to discomfort or because it simply doesn't work. Some people experiencing rapid weight loss have developed gallstones as a result, and your surgeon may advise that you have your gall bladder removed (cholecystectomy) at the same time as the gastric band is fitted.

This form of surgery is reserved for people who are obese and have a BMI of greater than 40 kg/M², or who have a BMI of 30-40 and also have a related health problem such as type 2 diabetes, high blood pressure or coronary heart disease. The operation may be available on the NHS if you fulfil these criteria and have failed to lose weight through diet and exercise alone, or with the help of anti-obesity drugs.

If performed privately, gastric surgery typically costs over £7,000. It is effective, however. Most people lose between 50 per cent and 65 per cent of their excess fat within two years. Weight loss is usually rapid for the first six months, when you lose 0.5-1kg per week, and then slows down. You can continue losing excess weight for three years or more, however, and the band usually remains in place permanently.

Most people are able to lose weight by following a suitable diet and exercise regime. I strongly recommend the book, Neris and India's Idiot-Proof Diet. They both lost five stone using their low glycemic approach.

Some people may need additional help in the form of anti-obesity drugs:

Orlistat works by blocking the action of digestive enzymes, known as lipases, to reduce the absorption of dietary fat by an average of 30 per cent. It is taken before, during or up to one hour after each main meal (up to three times a day) and is prescribed together with a weight management programme which includes a lower fat diet.

Trials show that overweight people taking orlistat can lose nearly twice as much weight, and maintain that weight loss over two years, compared with those following a diet alone. Almost half maintained a weight loss above 10 per cent after one year.

Sibutramine affects the levels of chemicals in the brain to make you feel fuller more quickly and reduce appetite so you eat less. In trials, 90 per cent of people who responded went on to lose over a stone in weight (7.7kg) by the end of a year. In comparison, of those taking inactive placebo, only 61 per cent managed to lose 2.4kg after 12 months treatment.

Rimonabant blocks receptors in the brain involved in appetite and cravings. Research has shown that people taking it lose around 6kg in a year compared with 1.6kg for those taking inactive placebo.

If you are obese, your doctor can advise whether or not drug treatment is likely to help you lose weight combined with a sensible diet and lifestyle changes, or whether you are a candidate for gastric banding.

For more information on gastric banding, see the British Obesity Surgery Patient Association (BOSPA) www.bospa.org