So what exactly is a gastric bypass, and why is it so expensive? And what might I expect the average gastric bypass surgery cost of surgery to be? This article will attempt to answer these and other questions about weight loss surgery. To answer the first question, a gastric bypass is a highly invasive procedure in which surgery is used as a tool for losing weight. Obviously, this represents an operations that causes serious trauma to the body, and most doctors recommend that you not request it unless you are truly seriously and chronically overweight. Seriously overweight generally means that you should be carrying around at least forty kilos more than you should be. Also, this condition should be chronic, meaning that you should have had that excess weight for at least five years, if not more. Under such conditions, so much excess weight represents a clearly definable reduction in your life span, and can justify the potential complications of surgery.