Alternative names: Bariatric Surgery.
Weight loss surgery works by restricting the amount of food the stomach can hold, and by decreasing the absorption of food in the stomach and small intestine. The two most common types of weight loss surgery are gastric banding and gastric bypass surgery.
All types of weight loss surgery result in a drastic reduction in stomach size above the band or bypass, reducing the amount that a patient can eat from about a quart of food to about a half-cup. The patient feels full much sooner, eats a lot less, and loses weight rapidly.
Gastric bypass surgery is the most common type of weight loss surgery and is both "restrictive" and "malabsorptive". By reducing stomach volume, food intake and therefore calorie intake is restricted. It also bypasses the top of the small intestine, decreasing the body's absorption of calories and nutrients from the food. The stomach and small intestine are each divided into two sections and the lower part of the small intestine is connected to the upper section of the stomach.
A more recent weight loss surgery technique is called gastric banding, a laparoscopic procedure that restricts how much food the stomach can hold without changing the way food is absorbed. An adjustable band is placed around the upper stomach to section off a small portion; periodic adjustments can be made by a surgeon through a port under the skin by adding/removing saline solution to tighten/loosen it. This controls how fast food passes through the restricted stomach pouch, and how soon the patient feels full. Gastric banding is less risky and less invasive than gastric bypass surgery, and it is often reversible.
Biliopancreatic diversion is more drastic than gastric bypass surgery and involves removing up to 70% of the stomach, and bypassing more of the small intestine. Biliopancreatic diversion with a duodenal switch, or simply the "duodenal switch surgery", is less drastic but still more severe than gastric bypass surgery.
Weight loss surgery is not for people who simply want to "lose a few pounds." It is a serious decision to take, and usually only recommended for either those who are severely obese (BMI over 40), or those who are moderately obese (BMI 35-40) and suffer from obesity-related medical conditions such as type 2 diabetes, coronary artery disease, hypertension, arthritis, or sleep apnea. However, Lap-Band surgery is approved for those with a BMI of at least 30 who have at least one obesity-related medical condition.
Diet and exercise should always be tried first.
After weight loss surgery, meal sizes shrink radically. They start with half a cup of food and move up to three-quarters or a whole cup. Foods should be high in protein, fats and nutrients, include vegetables, and be low in carbohydrates and sugar. Vitamin and mineral supplementation is generally required.
Gastric bypass provides immediate adverse consequences from overeating: nausea, vomiting, and flu-like symptoms. This is what makes it work for chronic over-eaters.
Gastric bypass surgery also causes malabsorption of some nutrients. The post-surgery diet must focus on supplementing specific nutrients that are lost, for example protein, vitamin B12, iron, and calcium.
As with any major surgery, there are potential risks and adverse outcomes. Short-term risks include:
Longer-term risks and complications include:
Weight loss surgery is not recommended for those who are obese due to a metabolic or endocrine disorder; are engaging in substance abuse; have untreated psychiatric disorders, heart disease or other medical conditions that increase the risks from surgery; women planning on becoming pregnant within 18 months.
Weight loss surgery is increasingly being used to manage type 2 diabetes. Controlling diabetes is directly related to losing weight; surgery has been shown to improve type 2 diabetes for most obese people and it can help patients normalize their blood sugar levels without diabetes medications.