I recommend that you discuss your concern with your doctor
. In general, even if a person does not eat they should still have regular bowel movements, since a lot of stool output actually consists of bacteria which just live in our gut. Eating a regular diet with lots of fiber helps ensure that you go regularly, as does making sure you stay well hydrated during the day. Diets that are high in fat and low in fiber will often cause people to go less regularly and have problems with constipation. The amount that you eat can relate to how often you go in that eating stimulates a reflex in the colon that keeps the bowels moving (that is why many people have a bowel movement after breakfast). Coffee can also stimulate the bowels and cause people to have a bowel movement. It sounds like you eat a healthy diet; eating a consistent amount of food may cause you to have more regular bowel movements, but it may also be that you have slightly irregular bowel movements. Increasing the amount of fiber you eat or taking a fiber supplement like metamucil may help. It would also be a good idea for you to discuss your concerns and your bowel habits with your doctor to make sure there is nothing else going on that could be concerning.