Headaches caused by not eating usually have the following factors: 1. The most common factor is hypoglycemia, which reduces the glycogen reserves in the body when the patient has not eaten. When the release of glycogen increases, there will be a negative nitrogen balance, which leads to a series of hypoglycemic reactions, and clinical symptoms such as dizziness, headache, peripheral weakness and discomfort will occur. 2. Headache when eating is also due to the presence of hypotension. When the patient does not eat, the body’s caloric intake is reduced, leading to a significant decrease in blood sugar and blood pressure. When the patient has hypotension, it will make the cerebrovascular transient blood supply insufficient resulting in headache. 3. Headache without eating is also related to spastic ischemia of the cerebral arteries. When the cerebral artery spasms, especially when the vertebrobasilar artery spasms, it will produce a transient ischemic response, and then clinical symptoms such as dizziness and headache will appear.