How Does Gastric Bypass Make You Lose Weight?
About Gastric Bypass
Gastric bypass is a form of bariatric surgery. A pouch about the size of a thumb is created just past the cardia (#6 on the diagram), and is then attached to the small intestine. The new pouch only holds about 15ml of food and drink, leading to a feeling of fullness after a very small amount of food. A normal stomach holds 400 to 500ml and can stretch to hold nearly 1000ml.
Gastric bypass is only performed on people who have a body mass index of 40 or higher, or a body mass index of 35 if they have a co-morbid condition like high blood pressure, atherosclerosis or type 2 diabetes. A National Institutes of Health Consensus Conference in 2004 found that bariatric surgery, including gastric bypass, is the most effective treatment for morbid obesity.
Why It Works
Gastric bypass surgery greatly reduces the size of the stomach and greatly limits its potential to stretch. If the attached small intestine fills too quickly with undigested food, nausea and vomiting can occur. To combat this, patients are instructed to eat small amounts of food. Sugary foods should be consumed with caution as they may produce lightheadedness, rapid heartbeat and diarrhea.
These changes in anatomy and the necessary changes in diet that follow produce dramatic weight loss. However, patients may slow the weight loss process or gain weight back if they snack between meals or eat enough to cause the connection between the stomach and small intestine to stretch. If the small intestine can hold more food, the patient can then eat more without nausea or discomfort.
Types
The small pouch may be totally divided from the rest of the stomach, or simply partitioned with surgical staples. Usually total division is done to prevent the two parts of the stomach from fusing back together during the healing process.
There are two types of gastric bypass generally performed: Roux en-Y distal and Roux en-Y proximal. In both procedures, part of the small intestine is attached to the new small pouch formed with the upper stomach. In a Roux en-Y proximal, an incision is made about 18 inches below the bottom of the original stomach, and it is then attached to the pouch. This preserves most of the small intestine, allowing for maximum absorption of nutrients. This is the most common type of gastric bypass surgery performed.
In the Roux en-Y distal procedure, the incision is made much farther down the small intestine, about 40 to 60 inches from the junction with the large intestine. Since so little of the small intestine is left, fewer nutrients are absorbed, along with fewer fats and starches, This results in both more weight loss and more potential complications due to nutritional deficiencies.
Tags: small intestine, Roux en-Y, attached small, weight loss, about inches