The harm of not eating carbohydrates to lose weight mainly contains: insufficient supply of carbohydrates leads to malnutrition, low blood sugar, gastrointestinal diseases and poor mental state. 1. Malnutrition: the human body does not intake of carbohydrates for a long time will cause malnutrition, resulting in low immune function. 2. Hypoglycemia: some people do not consume carbohydrates for a long time, blood sugar can not keep up, which may lead to hypoglycemia. 3. Gastrointestinal disorders: long-term diet without carbohydrates is very unfavorable to the function of the gastrointestinal tract, which may trigger intestinal peristalsis, cause constipation, and cause abdominal pain and bloating. 4. Poor mental state: carbohydrates will stimulate the body’s secretion of dopamine, the human body does not intake of carbohydrates for a long time may cause irritability, poor mental state, and even trigger depression. As a matter of fact, radical dietary weight loss methods are usually likely to cause harm to the body. Healthy weight loss methods should be low-energy balanced diet, such as using coarse grains instead of fine rice and noodles, meat as much as possible to use low-fat fish, chicken breast, etc., more vegetables, less oil and less sugar, in addition to the need to cooperate with the appropriate exercise and so on.