Gastric bypass combines restrictive and Malabsorptive techniques to produce weight loss:
Restrictive– the upper portion of the stomach is stapled to create a small ‘upper stomach’, or pouch about the size of a golf ball.
Malabsorptive – Most of the stomach is bypassed along with at least 150cm of proximal small intestine, necessitating vitamin and mineral supplementation .
Neuro-hormonal component – the intestine is cut or divided. The lower portion of this division (the long roux limb) is then lifted and joined to the new stomach pouch. The free end of the intestine (the biliopancreatic limb) is then joined to the remaining portion of the gut forming a ‘Y’ shape. Once the restrictive component of the bypass decreases, different mechanisms will kick in to maintain weight loss.
Food eaten passes into the pouch, which becomes full with small quantities of food, meaning that you will feel full quicker. Food then bypasses the remainder of the stomach and passes through the newly created opening into the long roux limb. This ‘replumbing’ of the intestine results as well in a degree of malabsorption of food and calories, aiding further weight loss.