This page explains the way an adjustable gastric band works.

The adjustable gastric band (AGB) was developed in the mid-1980s as an attempt to reduce the invasiveness, complexity and irreversibility of existing surgical solutions for obesity. A historical note on the development of the device can be found here.


The operation generally takes 45 minutes under general anaesthesia and involves the implantation of three components (see picture): A plastic band with an inflatable balloon on one side which is threaded around the stomach near its top end and then closed to form a ring, creating a small gastric pouch. The inflatable balloon is connected to a thin plastic tube which leads out of the abdominal cavity into the subcutaneous tissues; here it connects with an tough injectable port element.


This creates an implanted self-contained system which allows the gastric band to be inflated with liquid (usually water or saline solution) which is injected through the skin into the port by locating and piercing a tough rubber membrane with a specially designed needle.



The components of the AGB system, and the band in position, are shown in the image gallery that follows on the next page.


The size of the ring-shaped band (especially the tightness of its internal opening) is determined by the overall filling volume in the system. Most commercially available AGBs (there are around ten different models) can take up to 12 millilitres (mL) of fluid. Most patients experience good restriction of food passage into the stomach pouch with filling volumes between 5 and 9 mL. However, the optimal filling volume for any given patient is impossible to predict accurately beforehand, and moreover can vary over time. For this reason, most surgeons advocate gradually filling the AGB system with not more than 2 mL at a time, leaving an interval of several weeks between fills.


Most patients can expect to experience excessive restriction at some time, and if this fails to resolve, the patient may be unable to even drink water. This can develop into an acute medical emergency, necessitating an intravenous drip and a partial AGB unfill. Unfortunately, especially with overseas commercial operators, this is where many patients feel let down by their surgeons. Others complain that fees for fill adjustments are excessively steep (charges up to £350 per fill are reported).


Sometimes patients are happy with their restriction and have achieved good weight loss, but would welcome a temporary fill reduction (a "break") with a return to their previous restriction afterwards - this is something not possible with permanent "replumbing" operations. Although not always strictly medically indicated, a "break" of this sort may occasionally be acceptable on psychosocial or compassionate grounds.