Is it normal to lose weight after bypass surgery?

Yes: Yes, that's the primary purpose for the procedure.

Weight loss: it is normal to lose weight after CABG but it usually comes back. If you want to maintain the lower weight work with your doc on an appropriate diet and exercise program.

Yes: Are you talking about gastric bypass or cardiac bypass surgery. I would think in both conditions you lose weight since you are in the hospital, not getting full nutrition post operatively. In gastric bypass surgery, the calories offered are low compared to the needs. In cardiac surgery, you don't get advanced to full calorie requirements for a couple of days. Both cause weight loss