After my friend Nikki got weight loss surgery, I found out that there are a bunch of different surgeries.
Below is an illustration of a natural stomach. Scroll down for illustrations of three common and six less-common bariatric (weight loss) surgeries.

The Most Common Weight Loss Surgeries
In a Gastric Bypass operation, all but the very top section of the stomach is bypassed. A portion of small intestines is used to re-route the food.	A Gastric Sleeve is the removal of a large portion of the stomach, leaving a banana-shaped stomach.	An inflatable silicone device is placed around the top portion of the stomach. The patient feels full when the top portion of her stomach is filled.

Less Common Weight Loss Surgeries
Gastric Carpool surgery adds a special new tunnel, which allows high-calorie food a quick trip past the nutritional-absorption points in the stomach wall.	Gastric Bowtie surgery uses a crisp knot in the duodenum to restrict the flow of unneeded food.	The Gastric Button surgery uses an oversized coat button to divide and restrict the volume of the stomach. If necessary, a second button can be affixed to the patient's mouth.
The Gastric Escher procedure creates a gastrointestinal illusion, tricking the patient into thinking he is continuously eating.	The Gastric Labyrinth creates a maze of twisty little passages, all alike. Only a small portion of food ever exits the stomach.	An extreme, though temporary measure involves removal of any large meal, such as one from Chipotle, through a long opening with a surgical-grade Ziplock seal.