The most common types of gastric bypass surgery are the Roux-en-Y gastric bypass, or simply, the gastric bypass and the Gastric Band, or adjustable gastric banding system.
Gastric Bypass is the most common form of weight loss surgery in the United States because it results in reliable and maintainable weight loss with acceptable risks and minimal side effects. The concept behind it is to reduce the size of the stomach. In gastric bypass surgery, the surgeon staples off a large section of the stomach, leaving a small pouch. As such, you will not be able to eat as much as you could prior to surgery, since this small pouch can only contain a little food at a time. As a result, you lose weight. Additionally, because most of the stomach and some of the small intestine has been bypassed, i.e., food does not go through some of the sections of the stomach and intestines, some of the nutrients and calories will not be absorbed. To undergo this surgery, your body mass index must exceed 40 kg/m2.
Gastric bypass surgery will not be effective on the long run if it’s not consolidated by a lifelong commitment to making the necessary changes in lifestyle and diet. This includes regular exercise, maintaining an adequate intake of protein, taking vitamin and mineral supplements including a multivitamin, B12, iron and calcium (especially that these vitamins will not be adequately absorbed due to the bypass procedure), and avoiding sweets and fatty foods.
Weight loss surgery is considered successful when 50% of excess weight is lost and the loss sustained up to five years post-operatively. The expected weight loss in the first 1- 2 years after a Roux-en-Y Gastric Bypass is approximately 1/2 to 2/3rd of excess weight. 50% excess weight loss has been documented 10 years and more after Gastric Bypass.
Gastric Bypass Surgery achieves weight loss by decreasing intestinal absorption of food; instead of following its usual path, food bypasses a portion of the stomach and small bowel. In addition to surgical complications, some people experience long-term deficiencies of vitamin B12, folate, and iron. "Dumping syndrome," in which the consumption of sugar causes abdominal cramping and diarrhea, can also occur. Some people will also regain some weight in subsequent years.