My daughter was diagnosed with dermatomyositis about a year ago and I researched it as much as i could. Any stress can aggravate or cause a flare-up, which is what your doctor must have been referring to. If you are in "remission", a flare-up may occur post-surgery and require meds such as prednisone to suppress the rlare-up. I would ask your rhematologist if that were to happen, could you delay the steroids until your stomach has healed completely without any ill effects. I think the benefits of the weight loss would help you deal with less health concerns overall and be worth it overall. Just work closely with your rheumatologist - if they aren't supportive, find another rheumatologist! Good luck.