Excessive weight loss is usually associated with the following four types of metabolic diseases: First, diabetes. In diabetes, negative nitrogen balance occurs, so there is a metabolic syndrome of thirst, excessive drinking and urination, more intake but sudden weight loss, and therefore, the weight is reduced too quickly in a short period of time, and the most common disease is diabetes. Second, thyroid diseases, such as hyperthyroidism, the body’s basal metabolic rate is raised too quickly, so there is a negative balance, weight will also be reduced too much in a short period of time. Third, certain wasting diseases such as tumors and tuberculosis, such as pulmonary tuberculosis and lung tumors, can also cause excessive weight loss in the short term and at an excessive rate. Fourth, rare diseases such as blood system diseases and connective tissue diseases can also cause rapid weight loss in the short term.