Those dietary fibers that are energy-yielding nutrients insofar as they can be absorbed in the large intestine (more precisely the colon) by intestinal bacteria through fermentation.
These are mostly soluble fibers, but also some insoluble fibers.
E.g.: resistant starch, inulin, unavailable oligosaccharides, beta-glucans, pectins, or natural gums.
A number of fermentable fibers that have a prebiotic activity are referred to as prebiotic fibers.
It should be noted that one of the fermentation by-products (metabolites) is the formation of short-chain fatty acids. Another is the production of multiple gases, which explains why foods high in fermentable fibers can cause flatulence and stomach discomfort.