What is the surgery that you need? I would say that some surgeries can be dangerous if you are overweight. While bariatric surgery is still a surgery, it is pretty quick and therefore you will not be under anesthesia for too long. He other surgery you need may be one that would require you to be under for a lot longer, making it riskier. I would definitely ask the doctor, though. Those are just my guesses, but I am in no way a medical professional!