The most common factor is hypoglycemic reaction. When a person does not eat, it is a situation of excessive decomposition and consumption, but insufficient income, which will produce a transient hypoglycemic reaction, and when the blood sugar is less than 3.9mmol/L, there will be serious discomfort around the body. 2. Headache when not eating is also caused by insufficient blood supply to the cerebral blood vessels, and clinical symptoms and performance of headache and dizziness usually occur when the blood supply to the brain cells is inadequate and the cerebral blood vessels are deprived of oxygen. 3. This symptom is common during adolescence.