Why can't you eat before having surgery?

Because if you get sick from the anesthesia and vomit you could choke to death on your own vomit

"Why can't I eat or drink before surgery?

The likelihood that a patient will vomit during the anesthetic is increased with a short time interval between eating or drinking and the surgery. The most likely times for someone to vomit are going to sleep and waking up. Your risk of having a complication is increased if these events occur. The exception to this is emergency surgery, and special precautions will be taken to minimize the risk. Ask for the policy covering NPO (nothing by mouth) requirements at the location of your surgery. " -http://www.choosegha.com/aAnesthesia/FAQ_Before/wh...

"Why Shouldn't I Eat Before Surgery?

You are often told "don't eat past midnight the night before your surgery" but perhaps only a few sips of water. To better explain this to you, this is best said by the American Society of Anesthesiologists Guidelines on Sedation and analgesia by Non-Anesthesiologists" - http://www.yestheyrefake.net/anesthesia_full.htm

Risk for aspiration (choking on vomit) post anesthesia.

the first 2 answers are correct

vomiting due to the anesthesia

Because what happens if you have to use the bathroom to number1ornumder2.

They don't want you choking to death on vomit.

they want to sell you hospital food when it's over