Gastric bypass and other types of weight-loss surgery — also called bariatric or metabolic surgery — involve making changes to your digestive system to help you lose weight.Bariatric surgery is done when diet and exercise haven't worked or when you have serious health problems because of your weight. Some weight-loss procedures limit how much you can eat. Others work by reducing the body's ability to absorb fat and calories. Some procedures do both.While bariatric surgery can offer many benefits, all forms of weight-loss surgery are major procedures that can pose risks and side effects. Also, you must make permanent healthy changes to your diet and get regular exercise to help ensure the long-term success of bariatric surgery. If you qualify for bariatric surgery, your health care team gives you instructions on how to prepare for your specific type of surgery. You may need to have lab tests and exams before surgery. You may have limits on eating and drinking and which medicines you can take. You may be required to start a physical activity program and to stop any tobacco use.You also may need to prepare by planning for your recovery after surgery.