Digestion and Surgery
As food moves along the digestive tract, enzymes digest and absorb calories and nutrients. After you chew and swallow food, it moves down the esophagus to the stomach, where a strong acid continues the digestive process.
The stomach can hold about three pints of food at a time. When stomach contents move to the duodenum (first segment of the small intestine), bile and pancreatic juice speed up digestion. Most of the iron and calcium is absorbed in the duodenum. The jejunum and ileum, the remaining two segments of the nearly 20 feet of small intestine, absorb most of the remaining calories and nutrients. Food particles that cannot be digested in the small intestine are stored in the large intestine until eliminated.
How Surgery Promotes Weight Loss
Restriction: Gastric banding, gastric bypass and vertical sleeve gastrectomy are surgeries that limit the amount of food the stomach can hold by closing off or removing parts of the stomach. These operations also delay emptying of the stomach (gastric pouch).
Malabsorption: In gastric bypass procedures, a surgeon connects the stomach to a lower segment of the small intestine, bypassing the duodenum and some of the jejunum, thereby decreasing the absorption of calories and nutrients.
Though the results of these procedures are somewhat predictable and very manageable, side effects do occur.