In order to lose weight quickly, adopting a method of drinking only water and not eating for a day (also known as “water fasting”) is an extreme way of losing weight and may have a negative impact on your health. Although there may be weight loss in the short term, this weight loss is mainly due to the loss of water and muscle, not the loss of fat. In addition, long-term water fasting may lead to malnutrition, metabolic disorders, decreased immunity, dizziness, fatigue and other problems. ###Optimal duration of water fasting 1. **Short-term fasting (24-48 hours)**: If you insist on water fasting, it is recommended not to exceed 24-48 hours. Short-term fasting may have less impact on the body, but you still need to be cautious, especially if you have any health problems or are taking medicines. 2. **Long-term fasting is not recommended**: Long-term water fasting (more than 48 hours) may cause serious harm to the body, including electrolyte imbalance and impaired organ function. Therefore, long-term water fasting is not recommended. ### A healthier way to lose weight In order to lose weight healthily and sustainably, the following methods are recommended： 1. **Balanced diet**: Choose nutritious foods such as vegetables, fruits, whole grains, lean protein and healthy fats. Control caloric intake, but don't over-limit it. 2. **Moderate exercise**: Combine aerobic exercise and strength training to help burn fat and maintain muscle mass. 3. **Regular work and rest**: Ensure adequate sleep, which helps regulate metabolism and appetite. 4. **Drink plenty of water**: Keep your body hydrated, which helps metabolism and detoxification. 5. **Avoid extreme diet**: Extreme diet methods are often unsustainable and can easily lead to weight rebound. Only by choosing sustainable lifestyle changes can the effect of long-term weight loss be achieved. ### Summary Although the method of drinking only water and not eating for a day may bring about weight loss in the short term, it is not a healthy or sustainable way to lose weight. If you are considering fasting, it is recommended not to exceed 24-48 hours, and it is best to do so under the guidance of a doctor. A healthier way to lose weight is to achieve long-term weight management through a balanced diet and moderate exercise.