What are the chances of death sith gastric bypass surgery?

Very low: Most bariatric centers of excellence track their mortality rate. When given a choice, most patients gravitate towards a center with mortality rate < 2% (different from morbidity/complication rate). If you need bariatric surgery, do your homework and get the best center you can.

About 1/1000: The mortality (risk of death) after gastric bypass is about 1/1000, when done by a surgeon with good experience (a center of excellence surgeon). This is actually safer than the mortality rate for appendectomy (removal of appendix). The main causes remain pulmonary embolism (clots to the lung) or cardiac. Early walking and appropriate blood thinners are helpful.