I just wanna add that it makes a difference how big you are, because that usually means that you have bigger intestines and can store more, uh....fecal matter in them. It also means that it will take a lot more stuff to fill you up and give you the urge to defecate than it would a smaller person.
And to anyone who feels they aren't going enough, try drinking more water and eating bran cereal or oatmeal for breakfast everyone morning. No shitting (pun intended
) that's what doctors tell you to do.