I've been really interested in weight loss surgery nutrition and wanted to provide additional information about it. I had a really great class day last year at Johns Hopkins about the different surgeries/complications and even a patient who has lost a few hundred pounds.
Weight loss surgery basically restricts the amount of food that enters the stomach and causes a reduction of calories that are absorbed (so malnutrition is a big problem, i.e. you may look sickly/hair falls out).
That doesn't sound like a glamorous way to achieve a healthy weight, but sometimes after several diets/exercise options have failed and the patient is of a dangerously high weight, it can be a life altering challenge to live with.
Risks (this is also from WebMD's link above)
"Risks common to all surgeries for weight loss include an infection in the incision, a leak from the stomach into the abdominal cavity or where the intestine is connected (resulting in an infection called peritonitis), and a blood clot in the lung (pulmonary embolism). About one-third of all people having surgery for obesity develop gallstones or a nutritional deficiency condition such as anemia or osteoporosis. 3 4
Fewer than 3 in 200 (1.5%) people die after surgery for weight loss. 3
After a Roux-en-Y gastric bypass: 5 3
An iron and vitamin B12 deficiency occurs more than 30% of the time. About 50% of those with an iron deficiency develop anemia.
The connection between the stomach and the intestines narrows (stomal stenosis) 5% to 15% of the time, leading to nausea and vomiting after eating.
Ulcers develop 5% to 15% of the time.
The staples may pull loose.
Hernia may develop.
The bypassed stomach may enlarge, resulting in hiccups and bloating."
