Going to the bathroom and having a bowel movement as soon as you finish eating may be physiological, caused by increased intestinal peristalsis as a result of reflex after eating, or it may be due to the presence of a disease such as Irritable Bowel Syndrome (IBS). 1. Physiological, some people have the urge to have a bowel movement after eating, and then have a bowel movement. If the stool is normal, without abdominal pain, diarrhea and other abnormalities, usually considered a normal physiological phenomenon. It is mainly because the gastrointestinal tract fills up after eating, which reflexively causes increased intestinal movement and pushes the contents to the rectum, triggering defecation. 2. Pathologic, suffering from irritable bowel syndrome, ulcerative enteritis and other diseases. The intestinal mucosa is more sensitive and can be stimulated by food to cause bowel movements. Patients are usually accompanied by abdominal pain, diarrhea and other uncomfortable symptoms. This condition needs to be treated actively after the cause is clarified. Occasionally once after eating a meal on the large size may also be related to dietary cold, stimulation, unclean and other factors. Prolonged bowel movement once after eating, accompanied by diarrhea, emaciation and other conditions, should seek medical attention to clarify the cause of the disease and then treat without delay.