How does dietary fiber differ chemically from starch?

Dietary fiber is cellulose, which is indigestible to humans.

Starch is made up of the two polysaccharides amyloseand amylopectin. These are long complex glucose molecules which provide energy to the body more slowly than simple sugars.

By weight, starch is mostly amylopectin, which is soluble and easily digested.

Amylose is a prebiotic, is insoluble and is digested more slowly than amylopectin.