Roux-en-y gastric bypass has been the most commonly performed weight loss operation in the world over the last few decades. It is a highly effective, well proven operation at both decreasing your weight and also treating complications of your weight you may be suffering from (e.g. diabetes, sleep apnoea, high blood pressure, arthritis etc).
In gastric bypass two things are done to cause weight loss. Firstly a small pouch is created at the upper part of your stomach. This has the effect of decreasing the amount of food you can eat in a meal. Secondly, your small bowel is refashioned and joined to this pouch so that it looks like a Y shape. Firstly, this decreases the amount of time food will spend in contact with both the bowel, and also the enzymes that help digestion and absorption in your bowel. It also alters the way your body processes food, sugars, carbohydrates and hormones associated with feelings of fullness , also helping with long term weight loss.
A roux-en-y gastric bypass is performed as a laparoscopic (key-hole) operation through 5-6 small incisions. Firstly, the pouch is made using a stapling device. Secondly the small bowel is reconfigured into a Y shape. This involves dividing your small bowel in one place and making two joins one between stomach and small bowel, the second between two loops of small bowel. After this is done a test is performed to ensure the joins are watertight. You should expect to spend 2 nights in hospital after your operation (although on occasion some people go home after only one night).