There are two types of fiber, soluble and insoluble. Soluble fiber dissolves with water in the gut, while insoluble fiber adds weight to the stool and is simply excreted. Eating a diet high in fiber can help improve digestion and prevent constipation, but it can also lead to digestion problems if a person is not used to eating fiber. The Harvard School of Public Health recommends drinking plenty of water throughout the day to help soluble fiber dissolve and to prevent stomach cramping.