Diarrhea and oily stools are related to indigestion, small intestine malabsorption syndrome, pancreatitis and cholecystitis diseases. Some people have diarrhea and oily stools after consuming a large amount of fatty foods, and this condition is related to indigestion. Fatty foods are difficult to digest, and when the body has indigestion, it cannot digest and decompose fatty foods, so fatty foods are discharged in a semi-digested state, and fatty foods also have a laxative effect, so diarrhea and oily stool symptoms can occur. After the food is digested, the nutrients are mainly absorbed through the small intestine. Once the small intestine malabsorption syndrome occurs, the nutrients in the food cannot be absorbed, and then diarrhea and oily stool symptoms will also occur. Fatty foods are mainly digested through pancreatic juice and bile. When suffering from pancreatitis or cholecystitis, the secretion of pancreatic juice and bile will be affected, so it will not be able to break down the fatty foods consumed, and diarrhea and oily stools will also occur.