General surgery requires anesthesia, which is mainly divided into general anesthesia, local anesthesia, and intravertebral anesthesia. The reason why you cannot eat under general anesthesia is that you are not conscious after the anesthesia. If you eat before the anesthesia, there are food residues in your stomach, and if you vomit after the anesthesia, the food residues may reflux into your trachea and cause asphyxiation. In the state of general anesthesia without any consciousness, even if asphyxia occurs, it cannot be expressed, which may cause serious consequences, so doctors usually ask patients not to eat before general anesthesia surgery.