Constipation. Artwork showing hard, dry stools (brown) in the colon (or bowel) of a constipated person. Constipation is the infrequent, difficult passing of faeces (stools). It is not in itself harmful, but it may be a sign of a more serious underlying disorder, such as cancer of the colon. Constipation is usually caused by lack of fibre in the diet, which means the faeces do not have the bulk required to stimulate normal bowel movements. Eating more fibre and drinking plenty of fluids may help relieve the condition. Laxative drugs may be taken in some circumstances, although they themselves can disrupt bowel movements if taken for too long a period.