Anorexia nervosa is an eating disorder that usually refers to a condition in which weight is significantly lower than normal standards through intentional diet abstinence. There are many early clinical symptoms of anorexia nervosa, but there are not 10 precursors. The more common early symptoms of anorexia nervosa include behavioral changes and physical symptoms, mental disorders, and physical function changes: I. Behavioral changes: Patients will actively diet, resulting in a weight significantly lower than the normal standard, and there may be even if the weight is lower than normal, patients still often take self-induced vomiting, laxative abuse, excessive exercise, and other methods to reduce weight. Physical symptoms: Patients with anorexia nervosa are not interested in food, and if they are forced to eat, they may experience nausea and vomiting. Patients with anorexia nervosa often have a body weight of more than 15% less than the normal average weight, or a body mass index BMI of less than 17.5. Third, mental disorders: 1, body image anxiety: fear and anxiety about their own weight gain or imperfect body shape, which makes patients more and more do not want to eat, making anorexia gradually aggravated; 2, body image disorder: patients with anorexia usually have a distorted perception of themselves, even if they are already in a very thin body shape, they still think they are too fat; 3, mental illness: prolonged anorexia will also have an impact on The patient’s mental state, depression, anxiety and obsessive-compulsive symptoms unstable mood, irritability and social withdrawal and other mental disorders, some patients may even appear suicidal tendencies. Endocrine changes: Women with anorexia nervosa may experience amenorrhea and men may have symptoms of endocrine abnormalities such as hypogonadism. If the patient is prepubertal, he may show delayed development of secondary sexual characteristics; 2, malnutrition: due to insufficient nutritional intake, the patient may show symptoms of malnutrition such as dry and pale skin, low subcutaneous fat, loss of elasticity and luster hair thinning and falling off; 3, metabolic disorders: imbalance between nutritional intake and output may cause various electrolyte disorders, such as hypotension, low body temperature, bradycardia, palpitations, anemia, edema, asymptomatic hypoglycemia, hypokalemia, etc.; 4. Other: uneven dietary intake for a long time may also cause patients to develop gastrointestinal disorders, cardiopulmonary insufficiency, abnormal liver and kidney functions and other organ function abnormalities.