IBS = Irritable Bowel Syndrome. Certain foods, as well as stress, can be independent triggers. It sometimes manifests as diarrhea; it sometimes manifests as constipation; sometimes people have both. A gross oversimplification is that everyone should be pooping a banana-sized stool. If you are not, it could be something you are eating or feeling. One doesn't have to overthink this unless one is experiencing defecation problems or gut discomfort.