Yes, it is bad if you eat before surgery.
You should have been asked not to eat 8 - 12 hours prior to your surgery. If you are going under anesthesia, the anesthesia paralyzes your entire body, and if you have ate, you might vomit which will cause difficulty breathing or even in some cases, death. If you are having surgery somewhere on your lower stomach, eating before the surgery may lead to infection. Overall, they want you to not eat for 8 - 12 hours prior to surgery only for safety. I wouldn't even drink water, because if you are put under anesthesia, there is an increased risk of vomiting.