Light fasting is defined as consuming only 500 kcal (for girls) or 600 kcal (for boys) of energy per day on 2 non-consecutive days of the week, and eating freely and without control for the remaining 5 days. It may lead to the development of digestive disorders, constipation, malnutrition, loss of muscle mass and other hazards. 1. Digestive disorders: Due to the small amount of food intake during light fasting, the gastrointestinal tract is mostly in fasting, if the increase of gastric acid secretion, when in the state of starvation, it is easy to lead to gastrointestinal dysfunction, in the long run, peptic ulcers, chronic gastritis, and other digestive disorders may occur. 2. Constipation: Due to the light fasting period, eating less or no food, the body does not intake of starch and fat, there is no food raw materials, can not form stools, resulting in the emergence of constipation; when the end of the light fasting, start a normal diet, then the stomach and intestines may receive the wrong signals, gastrointestinal peristaltic function will be weakened, and constipation will still occur. 3. Nutritional deficiencies: Due to long-term adherence to light fasting, resulting in nutritional deficiencies, the freshly squeezed fruit and vegetable juices consumed during the fasting period can not provide the full range of nutrients needed by the human body, especially carbohydrates, fats, and other nutrients that provide energy, which may lead to the emergence of nutritional deficiencies. 4. Muscle mass decline: long-term light fasting, exercise decline, muscle does not get exercise, may also lead to muscle mass decline. Therefore, light fasting is also in moderation, to avoid long-term light fasting damage to the body.