Loss of appetite and weight loss may be caused by gastrointestinal diseases, liver diseases and biliary and pancreatic diseases, etc., but the specific causes need to go to the hospital for relevant examinations before they can be clarified. 1. Gastrointestinal diseases: such as inflammatory bowel disease, gastrointestinal tumors, etc., will lead to loss of appetite and weight loss, accompanied by abdominal pain, diarrhea, black stools, etc., need to consult the doctor, improve the gastrointestinal microscopy and other tests to further clarify the diagnosis. 2. Liver diseases: such as acute and chronic hepatitis, liver cirrhosis, liver cancer, etc., which will cause liver function abnormalities and digestive dysfunction, resulting in loss of appetite and weight loss, accompanied by abdominal pain, jaundice and edema, etc., and can be diagnosed by liver function, ultrasound, nuclear magnetic resonance imaging, etc., according to the instructions of the doctor. 3. Biliary and pancreatic diseases: such as chronic pancreatitis, chronic cholecystitis, gallbladder cancer, bile duct cancer, pancreatic cancer, etc., in addition to the above symptoms, may also be accompanied by abdominal pain, jaundice and diarrhea, etc., and need to follow the doctor’s instructions to improve the CT enhancement, nuclear magnetism and other tests to clarify the diagnosis. There are many reasons for loss of appetite and weight loss, so it is recommended to consult the doctor in time, improve the examination to clarify the cause of the disease and give targeted treatment.