The latest surgical technique to combat morbid obesity. There are numerous slight modifications used, but the most common type in use today is the gastric bypass Roux-en-Y operation (Roux was the French surgeon who developed the technique).
Basically, when a patient's body fat is high enough for them to be categorized as morbidly obese, they become a candidate for this rather extreme solution to their problem (surgery is never something to take lightly). The general consensus amongst the medical profession being that obesity will kill you for certain, while surgery might save your life.
Using this technique, the surgeon cuts most of the bottom portion of the stomach loose and sews up the remaining part, creating a small, golf ball sized pouch just below where it meets the esophagus. The upper intestine is also cut a few inches below the lower stomach, and is brought up to connect to the new, much smaller stomach. The lower stomach is reconnected to the intestines, but is now bypassed from the flow of food. In case the surgery ever has to be reversed, the lower stomach is still there, ready to be reattached.
This surgery forces people to feel full much sooner while eating, so they intake less calories. It is almost certain to cause rapid weight loss, since the patient simply cannot eat as much as they once could.
I feel compelled to tell people that gastric bypass surgery is not cosmetic surgery. It is not intended to help you lose a few pounds, or make you pretty, or buff, or sexy, or popular. It is a desperate measure to make you lose weight, and thereby save your life. But in a world full of diets that just don't work, this is a technique which almost always does succeed in causing weight loss and increasing the overall health of the patient. Happiness is just a nice side effect.