Fiber is a type of carbohydrate found in plant foods such as fruits, legumes, vegetables, and whole-grains, which cannot be fully digested. Commonly referred to as dietary fiber or roughage, fiber adds bulk to a diet, assisting digestion and bowel movement functions.
Eating foods that are high in fiber tend to make you feel full, which helps people who are dieting to lower their consumption of food; therefore, their calorie intake is reduced resulting in weight loss. Since fiber cannot be absorbed by the body, it contains no calories.
There are two types of fiber or roughage, as it is sometimes called: water soluble (i.e., gums, pectins, and mucilages) and water insoluble (i.e., cellulose, hemicelluloses, and lignins). Each plays a role in providing health benefits.