This is a restrictive technique which only affects the stomach. It consists in the removal of part of the stomach, leaving this organ shaped like a narrow tube, with a capacity of around 150cc. There is a restrictive effect, and appetite is thus reduced.
Besides, there is a reduction in the production of a hormone called ghrelin, which increases appetite; when there is less ghreline, there is lower appetite.
Its advantage is that it does not alter the absorption of food or other substances, as it does not act upon the intestine. This is used as a final technique, or as the first step before conducting a bypass in very obese patients, or those with a high surgical risk (transplanted patients, etc.).