Drinking only water every day without eating is often referred to as "water fasting". Although short-term water fasting may not cause obvious harm to health immediately, long-term without food intake will cause the body to lack necessary nutrients, which may cause a series of health problems. The length of time that health is maintained varies from person to person, and usually depends on factors such as the individual's weight, health status, and activity level. Generally speaking, some people may feel able to tolerate it within a few days to a week, but over time, the body will begin to show signs of lack of energy and nutrition, which may lead to: 1. **Decrease in physical strength**: Insufficient energy supply leads to fatigue and weakness. 2. **Malnutrition**: Lack of necessary protein, vitamins and minerals may affect the immune system, muscle function, etc. 3. **Risk of dehydration**: Although drinking water can prevent dehydration, long-term without food intake can also affect electrolyte balance. 4. **Cardiovascular problems**: Lack of nutrition in the human body may cause heart health problems. It is not safe to fast for a long time. It is recommended to consult a doctor or nutritionist before making any dietary changes to ensure physical health and safety.