Fatty stools may be caused by conditions such as lipase inhibitors, pancreatitis, and small intestinal malabsorption syndrome. 1. Lipase inhibitors: Lipase inhibitors such as oseltamivir will inhibit the pancreas from secreting lipase, resulting in the inability to break down lipids in the digestive tract, and the intestines will not be able to absorb lipids, which may ultimately result in greasy stools. 2. Pancreatitis: The pancreas can secrete lipase, which degrades lipids in food, so that lipids can be turned into small molecules and be absorbed by the intestines. However, in pancreatitis, the pancreas is unable to secrete the enzyme lipase normally, which prevents lipids from being absorbed by the body, and greasy stools may be formed in the end. 3. Small intestinal malabsorption syndrome: The small intestine is the main part of the digestive tract that absorbs fat. If the absorption is impaired and the lipids are broken down but still not completely absorbed, greasy stools may be formed in the end. If any of the above situations occur, please consult a doctor in time for reasonable and standardized treatment.