Body thinness may be caused by malnutrition, hyperthyroidism, diabetes and other reasons. 1. Malnutrition: If the nutritional intake is insufficient for a long time, it may lead to malnutrition of the patient, and the supply of protein as well as energy needed by the body is insufficient, which causes weight loss, and then the body will be thin. 2. Hyperthyroidism: when the patient’s thyroid hormone secretion is too much, it is easy to lead to the body of the gastrointestinal tract peristalsis function accelerated, the food stays in the gastrointestinal tract for a shorter period of time, which is not conducive to the absorption of nutrients, and at the same time, the consumption of energy increases, the metabolism rate is higher, so that the patient appears to have a thin body symptoms. 3. Diabetes: Due to insufficient insulin secretion in diabetic patients, high blood glucose concentration, the body’s utilization of glucose obstacles, resulting in the breakdown of body fat and protein to provide energy for the human body, and at the same time, due to the increased osmotic pressure of the blood, resulting in the loss of water, which further reduces body weight, will also lead to the patient to experience the symptoms of thin body. Body thinness may also be caused by other reasons, such as tumors, mental and psychological disorders, etc. It is recommended that the patient consult a doctor in a timely manner to clarify the cause of the disease and then carry out treatment under the guidance of the doctor.