healthy adult can generally go from a few days to a few weeks without food, but the specific time varies from person to person, depending on factors such as personal body reserves, health status, and living environment. Generally speaking, the body will consume glycogen reserves first, and then turn to fat and muscle tissue for energy. However, long-term non-eating can lead to malnutrition, a damaged immune system, and other health problems. Therefore, no matter what reason you are considering not eating, it is best to consult a medical professional. In addition, pay attention to the balance of electrolytes, because drinking water alone may cause electrolyte imbalance, which may cause serious health problems.