The initiation of puberty depends primarily on genetic factors, but other factors also influence the timing and rate of puberty onset and development, including geographic location, light hours, physical and nutritional status, and psychosomatic factors. For example, children in families with an earlier onset of puberty reach puberty earlier, and girls near the equator, at lower altitudes, in cities, and who are mildly obese have an earlier onset of puberty. In 1974 Frisch argued that a girl must reach a decisive weight (47.8 kg) before the first menstrual period may occur. 1991 Maclure argued that more important than total body weight is the need for a certain percentage of body fat (16.0% to 23.5%), which also reflects the influence of nutritional status. In recent years, the discovery and study of leptin (leptin) has led to a renewed awareness of the importance of the relationship between body fat and reproductive function. Leptin is a peptide secreted by fat, bound to proteins in the blood, and able to act on neurons in the central nervous system that regulate feeding and energy balance. The following experimental findings support the role of leptin in reproductive physiology: 1, leptin promotes pubertal development in rodents. 2. Leptin levels are elevated in adolescent boys. 3, athletes, anorexia nervosa and delayed puberty have lower leptin levels. 4, lack of leptin rats can still have normal sexual development, but can only be maintained in the prepubertal state, and no ovulation phenomenon. After leptin application, their reproductive capacity will be restored. Therefore, it is reasonable to assume that a central mechanism triggers the maturation of the hypothalamic-pituitary-ovarian axis, which stimulates growth and increases body weight to the necessary basal weight, while also increasing body fat content. Leptin levels increase gradually during childhood until they reach a certain threshold before reaching puberty, and the gradual increase of leptin levels to reach a certain threshold requires a certain amount of adipose tissue as the basis. Excessive leanness due to anorexia nervosa or fat loss without myasthenia gravis can seriously affect growth and development and even cause amenorrhea. At present, there are several methods to measure whether the weight is normal: 1, standard weight comparison method: adult height above 165cm: normal weight (Kg) = height (cm) – 100 adult height below 165cm: normal weight for men (Kg) = height (cm) – 105 normal weight for women (Kg) = height (cm) – 100 The weight calculated according to the above method is within 10% of the normal weight. Weight more than 10% of the standard weight is overweight, weight more than 20% of the standard weight is obese. 2, body mass index: weight (block) index (Body mass index, BMI, also known as the Quetelet index) is the ratio of weight (kg) and height squared (m2). BMI15～19 is normal; BMI19～22 is good; BMI＞24 is overweight; BMI＞27 is obese for women, BMI＞25 is obese for men; BMI30 is equivalent to 30% overweight BMI is the current international common weight evaluation method. 3, waist hip ratio (waist: hip ratio, WHR): in recent 20 years found that the fat distribution of different parts, the impact on metabolism is different, so according to the distribution of fat will be divided into male type and female type obesity, with waist hip ratio for identification. Waist circumference is the circumference of the abdomen at the level of the umbilicus when lying down, and hip circumference is the circumference at the level of lying down, and the ratio of the two is WHR. WHR>0.85 is male type obesity, and WHR>0.75 is female type obesity.