International Sports Sciences Association (ISSA) Fitness Nutrition Practice Test

Dietary fiber is classified as a carbohydrate that is not digested or absorbed by the human digestive system in the same way that other carbohydrates are. Unlike simple sugars and starches, which get broken down into glucose and absorbed into the bloodstream, fiber predominantly passes through the gastrointestinal tract intact or only slightly altered.

The two main types of dietary fiber - soluble and insoluble - have different roles. Soluble fiber can dissolve in water and forms a gel-like substance in the gut, which can aid in digestion and help regulate blood sugar levels. Insoluble fiber, on the other hand, does not dissolve in water and adds bulk to stool, helping to promote regular bowel movements. However, neither form is digested in the traditional sense, as they do not provide calories or nutrients by breaking down into usable forms for the body.

This understanding of dietary fiber's role highlights its significance in promoting digestive health, rather than acting as a source of energy or nutrients. Therefore, the answer that fiber is not digested or absorbed aligns with the fundamental physiological processes of human digestion and metabolism.