Weight loss may be caused by physiological factors such as insufficient food intake or excessive energy consumption, or pathological factors such as digestive system diseases, endocrine diseases, malignant tumors and other causes can lead to. 1. Physiological factors (1) Insufficient food intake: For example, if there is difficulty in swallowing or picky eating, and if there is insufficient food intake during the growth and development cycle, weight loss may be caused by the fact that there is too little food via the mouth to satisfy the energy needed for normal cell growth and development. (2) Increased energy consumption: If aerobic training such as jogging and anaerobic training such as plyometrics are carried out every day, and diet is strictly controlled, so that energy intake is less than energy consumption may also lead to weight loss. 2. Pathological factors (1) Digestive system diseases: For example, chronic gastroenteritis, cholecystitis and other digestive diseases may lead to weight loss because the nutrients in the body cannot be completely digested and absorbed. (2) Endocrine and metabolic diseases: for example, patients suffering from diabetes, hyperthyroidism and other metabolic diseases, due to poor metabolic function leads to incomplete absorption of nutrients, resulting in weight loss. (3) Malignant tumors: patients suffering from malignant tumors, because of the constant proliferation and differentiation of cancer cells in the body need to consume a lot of energy leading to the apoptosis of normal cells in the body, which will lead to weight loss. Patients who have been losing weight are recommended to go to the hospital in time for examination to clarify the cause of the disease, and then targeted treatment to avoid delaying the condition.