Diseases that lead to sudden and significant weight loss within a short period of time, including organic diseases and psychological factors, as follows: 1, organic diseases: diabetes, hyperthyroidism, malignant tumors, especially malignant tumors involving the gastrointestinal tract, affecting the digestion and absorption of nutrients, are likely to lead to sudden weight loss; 2, psychological factors: due to stress, resulting in a poor diet, poor digestion, absorption and weight loss. 2. Psychological factors: Due to the stressful condition, it leads to poor diet, poor digestion and absorption, and causes weight loss. Once there is a significant drop in weight within a short period of time, it is important to consult a hospital in a timely manner, thyroid function, blood glucose levels, glucose tolerance test testing, but also pay attention to check the tumor markers and imaging tests, and then combined with the symptoms targeted to find the possible causes, after the diagnosis should be timely treatment.