Constipation may result from several causes including a poor diet, poor bowel habits, or problems in elimination of stool, whether physical, functional, or voluntary. The following are some of the most common causes of constipation. Poor diet: Eating foods rich in animal fats (dairy products, meats, and eggs) or refined sugar but low in fiber (whole grains, fruits, and vegetables). Inadequate fluid intake: Not drinking enough water can lead to hard dry stools.