Contrary to popular belief (and what you may have been told by other clinics), a gastric bypass is not a malabsorptive procedure. Exactly how the gastric bypass procedure produces such impressive weight loss is not yet fully understood but studies have shown that although an element of calorie malabsorption is present early after surgery, this is relatively short-lived. Instead, it seems that RYGB has a major impact on various gut hormones, some of which are involved in appetite regulation.
Levels of ghrelin – an appetite stimulant – have been found to fall after gastric bypass, which may help to explain why patients experience such a marked loss of appetite. It is also known that individuals who have undergonegastric bypass have profound changes in taste and food preferences, which may further contribute to weight loss.
Restriction
The small pouch (sometimes called a micro-pouch) made by the surgeon, represents only about 5% of the total stomach volume. This means that you can only eat a very small amount of food before feeling full. Less food intake means fewer calories and fewer calories means weight loss.
Effect on gut hormones
For many years it was thought that gastric bypass results in significant calorie malabsorption, ie. calories from food and drink could not be absorbed across the wall of the bypassed section of small bowel.
