Malabsorption of calories and nutrients occurs via two mechanisms. First, the bile and pancreatic fluids and other digestive enzymes eventually join the ingested food – but at a point in the distal small intestine (ileum) where there is much less chance for complete breakdown and absorption, approximately 50–100 cm from the colon. The undigested fat consumed by the patient can cause gas and loose, foul-smelling bowel movements. The second mechanism through which malabsorption occurs is by decreasing the amount of small intestine through which the ingested food passes. With so little of the intestine with which food is in contact, less nutrients can be absorbed [1].

Patients also experience changes in gut hormones in a manner that impacts hunger and satiety as well as blood sugar control. The BPD/DS is considered by many to be the most effective surgery for the treatment of diabetes and to have the greatest total amount and greatest sustained long-term weight loss [1].

The BPD/DS can be performed laparoscopically, but this operation is more demanding technically than the Roux-en-Y gastric bypass and should only be performed by fellowship-trained surgeons in experienced centers.