Why does cellulose not provide energy to the body?

Cellulose does not provide energy to the body primarily because it is not digestible by human enzymes. Cellulose is a type of fiber found in the cell walls of plants and is classified as a polysaccharide. The structure of cellulose is such that it consists of long chains of glucose molecules linked by beta (1→4) glycosidic bonds. Humans lack the necessary enzymes, specifically cellulases, to break these bonds and therefore cannot digest cellulose.

This indigestible quality means that cellulose passes through the digestive system largely intact, contributing to a feeling of fullness and aiding in digestion, but it does not contribute calories or energy to the body. Dietary fiber, such as cellulose, plays an essential role in maintaining digestive health and regulating blood sugar levels, but it does not provide the energy derived from carbohydrates, proteins, or fats that the body can utilize.