Decreased appetite is not necessarily a precursor of serious illness, it may be caused by physiological factors such as mental stress; it may also be caused by gastritis, hepatitis, hypothyroidism and other mild diseases; but it may also be a precursor of serious illnesses such as stomach cancer. 1. Physiological factors: if the recent mental stress, physical overwork, may lead to decreased appetite, which is a normal physiological phenomenon, may be accompanied by symptoms such as mental fatigue, dizziness and so on. 2. Gastritis: If you often smoke and drink alcohol, eat unhealthy food such as barbecue, fried food or spicy and stimulating food such as chili, mustard, etc., it may induce gastritis, resulting in a decrease in appetite; it may also be accompanied by symptoms such as acidity in the stomach and stomach pain. 3. Hepatitis: Viral, bacterial, parasitic and other pathogenic infections may induce hepatitis, resulting in impaired liver function and decreased appetite. Symptoms such as abdominal distension, aversion to greasy food, and liver enlargement may also occur. 4. Hypothyroidism: Hypothyroidism may be induced by lack of iodine or insufficient synthesis of thyroxine in the body, which may lead to loss of appetite of the patient; and there may also be symptoms of pallor, swelling and indifference. 5. Stomach cancer: Helicobacter pylori infection and long-term incorrect eating habits may induce stomach cancer. Patients may have symptoms such as loss of appetite, epigastric pain, nausea and vomiting, and weight loss. If appetite decreases and physiological suggestions are excluded, patients are advised to go to hospital for relevant examination to clarify the cause of the disease, and then follow the doctor’s instructions to treat the cause of the disease.