Duodenal switch (DS) operation results in the highest success rate of all weight loss surgical procedures. Patients, over time, will experience some weight gain many years after DS procedure. There are a number of suspected mechanisms that may be responsible for the weight gain:

1-Ageing may slow the metabolism and the activity down.

2-Over time patients may not be as adherent to healthy dietary and lifestyle changes as they may have been immediately after surgery.

3- Hypertrophy of the alimentary and common channels over time increases in surface area f allowing greater caloric absorption leading to increased weight gain.

It has been demonstrated in bowel resection studies, as well as rat studies, that the nutrient stimulated regions of small intestine increase villus height and total weight, crypt depth and proliferation as well as wall thickness, as an adaptation to compensate for the loss of absorptive capacity in the resected bowel. This observation may be applied to DS procedure as seen in histological slides from a patient who had to have an operation done requiring bowel resection. The segment of the bowel resected included the junction of the biliopancreatic, common and alimentary limbs.