For very obese people who need more than diet and exercise, weight loss surgery can be lifesaving.
Depending on the type of weight loss surgery, patients often lose 30% to 50% of their extra weight in the first 6 months after surgery. Yet weight loss surgery is major surgery and does come with small but serious risks.
Weight loss surgery works in two ways: by restriction and malabsorption.
Surgeries that use restriction work by preventing the stomach from stretching to full size. Normally, the stomach can hold about 6 cups of food. After weight loss surgery, the stomach can hold only a cup or so. This results in feeling full faster, eating less, and losing weight.
Some weight loss surgeries divert food around a section of intestine as well as shrink the stomach. By skipping some of the intestine, fewer calories are absorbed. This leads to weight loss.
Most weight loss surgery today is laparoscopic. In laparoscopic surgery, the surgeon makes five to six small cuts in the belly wall. He inserts tiny tools and a camera through these holes, then operates while watching a video screen.
In open surgery, the surgeon makes one large cut along the middle of the belly. This is sometimes necessary, when the surgery cannot be done laparoscopically.
The surgeon divides the stomach into a large portion and a much smaller portion. He then staples the small stomach portion to make a small pouch.
The surgeon then disconnects the stomach pouch from the first part of the small intestine (the duodenum). The surgeon reconnects the stomach to the second part of the small intestine (the jejunum).This is the bypass.
After gastric bypass, you feel fuller after eating less food, so you lose weight. The bypass also makes you absorb fewer calories, so you lose more weight.
This is the second most common weight loss surgery. Using laparoscopic tools, the surgeon places an inflatable silicone band around the upper stomach. He tightens the band so the stomach becomes a small pouch with a narrow outlet.
Afterward, the patient feels full faster, eats less, and loses weight. The surgeon can tighten or loosen the band to minimize side effects and improve weight loss.
Gastric banding is considered the least invasive weight loss surgery. Surgeons can reverse the procedure, if necessary.
Biliopancreatic diversion is similar to Roux-en-Y gastric bypass:
Like a Roux-en-Y gastric bypass, the surgeon divides the stomach and creates a small pouch.