Anorexia nervosa is an eating disorder that is intentionally caused and maintained by oneself, characterized by loss of appetite, weight loss, and even anorexia caused by dieting, often resulting in malnutrition, metabolic and endocrine disorders, and somatic dysfunction. The most basic symptom of anorexia nervosa is anorexia, extreme lack of appetite and physical wasting. The symptoms are mainly related to psychological factors and are not caused by organic diseases of the digestive system. The age of onset of this disease is 10-30 years old, mostly 15-23 years old. Female patients are about 10-20 times more likely than males. The incidence of anorexia nervosa shows a significant increase or decrease due to changes in social mores and lifestyles. Acute trauma or persistent depression of mood may lead to this disease under certain conditions. The main clinical manifestations of the disease are: a psychological and behavioral pattern of intentional dieting for fear of obesity at the beginning, followed by unlimited restriction of diet, rapid weight loss, and refusal to increase the amount of food even though it is as thin as a malignant disease, even to the extent of losing weight without restriction to the point of deformation and death, and still feeling too fat. Refusal to maintain weight in its age and height equivalent to the minimum, so that some patients are as thin as wood, unable to get up, some people die of starvation, some use exercise, vomiting, diarrhea and other means to reduce weight, sometimes appear overeating, after eating vomiting, weight loss of more than 25%. Nausea, dizziness, weakness and sometimes fainting often occur due to hypoglycemia. The skin is dry, pale, with poor elasticity and thin subcutaneous fat, and the skin is edematous due to hypoproteinemia and other signs of extreme malnutrition. It is accompanied by severe endocrine dysfunction, amenorrhea in women, and decreased libido or impotence in men. If it occurs before puberty, pubertal development slows down or even stagnates, breast dysplasia, male secondary sexual characteristics do not develop, and genitalia are infantile. These patients often have emotional instability, anxiety, insomnia, obsessive-compulsive ideas, and in some cases, secondary depressive pathology, and in severe cases, suicidal ideas and behaviors. What should not be overlooked is that many young girls are generally unaware of anorexia nervosa, and those who deliberately diet in the blind pursuit of slimming have suffered from anorexia nervosa and dystrophic muscular atrophy to varying degrees. Criteria for diagnosing anorexia nervosa (1) lower than the standard weight of the same age and height by more than 15%, or 25% less than their original weight; (2) the pursuit of slimness, intentional control of diet, willing to starve; (3) female menopause for more than 3 months; (4) slow heartbeat, vomiting, etc.; (5) no other physical diseases or schizophrenia and other diseases; (6) the age of onset of 10 to 30 years. The treatment of anorexia nervosa mainly includes the following aspects: (1) Psychological treatment: first of all, we should obtain the cooperation of the patient, understand the causes of its onset, and give cognitive treatment and behavioral treatment. (2) Somatic support treatment: supply high-calorie diet for the characteristics of low feeding, and give intravenous infusion or high intravenous nutrition treatment for those who are accompanied by vomiting or refusing to eat. Supplementation of multivitamins and hormone therapy can be given to those with endocrine changes. (3) Promote appetite: under the observation of physician, inject insulin 2-6 units half an hour before meal until weight recovery. (4) Psychotropic medication: antidepressants, antipsychotics lithium salts, antiepileptics, and anti-anxiety drugs can be used for the treatment of this disease. Commonly used are sulpiride 200-400mg/day, cyproheptadine 12-32mg/day, amitriptyline 150mg/day, new antidepressants are more effective for those with bulimia induced vomiting. (5) Change of concept. Now popular slim, thin for beauty, is a trend. And the identity of fat and thin, firm and slim or not, is changing with the direction of public opinion. Fat as beauty and firmness as beauty are widespread in history, or in some countries and regions now. In my opinion, young girls are at the stage of physical development, do not blindly lose weight and over diet. Regardless of the trend, health is always beautiful, and firm and plump is more conducive to resistance and fertility, but also more sexy, and more likely to enjoy a wonderful sex life later.