Weight Loss Surgery Explained
The food that is eaten is stored and broken down in the stomach and then absorbed in the small intestine.
Bariatric or weight loss surgeries target these two sections of the digestive system to achieve weight loss and reduce the risk of obesity-associated diseases. The physiological mechanisms behind Bariatric surgeries can be broadly described as follows:
- Restrictive: These surgeries help limit the amount of food that the stomach can be stored; thereby limiting the intake of food and thereby the amount of calories consumed.
- Hormonal/metabolic: These operations cause changes to the hormones produced by the gut which result in suppression of appetite, increase energy expenditure, reduced conversion of calories to fat and more effective regulation of blood sugar levels.
- Malabsorption: These surgeries limit the amount of nutrients and calories that the body absorbs by bypassing a section of the small intestine.
Adjustable gastric banding is a purely restrictive procedure as the storage size and outlet of the stomach is restricted by the band.
Sleeve gastrectomy is considered as a combined restrictive and metabolic operation where the size of the stomach is reduced with 75% of the stomach removed and thereby decreasing its storage capacity. There are also hormonal changes occurring through removal of (most of) the section of the stomach that produces hunger hormones and the increased speed of food being delivered to the latter part of small bowel.
Roux-en-Y gastric bypass is primarily a restrictive and metabolic procedure with a mildly malabsorptive component. The amount of food stored is limited by the small pouch created at the top of the stomach and then it is bypassed away from a section of the small intestine which leads to hormonal changes. There is also a small limiting effect on the absorption of nutrients.