A Laparoscopic Roux-en-Y Gastric Bypass is a type of bariatric surgery or surgeries that we do to treat obesity and the diseases related to obesity.
Laparoscopic means that the surgery is done in a minimally invasive approach, meaning that we use several small incisions, usually 4 or 5 small incisions, to re-align the flow of food through the gastrointestinal tract.
Gastric bypass implies that we are bypassing a large portion of the stomach. We cut the top portion of the stomach away from the rest of the stomach, then we sew a part of the middle of the intestine to the top portion of the stomach. So after surgery, when someone drinks or eats their food, it does enter the top of the stomach but then it goes straight into the middle of the intestine, therefore, bypassing the stomach and the very top portion of the intestinal tract.
What that leads to is several different hormonal and other biologic function changes in the body that make people less likely to eat, or want to eat, or have the drive or desire to eat, and to limit cravings for foods that are high in sugars or carbohydrates, things that we know are not advantageous for weight loss. It seems to also have effects to directly change how the body handles calories, and so may directly have effect for weight loss.
Some of the older ideas about how bypass surgery works, including malabsorption and restriction which is, you know, you have a smaller stomach so you can't eat as much at one time, are really not the main thrust of how these surgeries work.
As we've learned more about the biology surrounding bariatric surgery, they do play minor roles, but the main change, the main way that we encourage weight loss after surgery is by changing the body's basic physiologic functions.