The present invention relates to a dietary composition produced by a process involving extruding a protein containing product and water through an extruder (e.g., at about 50-about 450 rpm and at a temperature of about 40.degree. to about 120.degree. C., wherein the residence time of the protein containing product (e.g., whey protein isolate) in the extruder is about 15-about 90 seconds) to produce the dietary composition, wherein the dietary composition contains partially denatured protein containing product or totally denatured protein containing product or mixtures thereof. The present invention also concerns a food product containing at least one food ingredient and a dietary fiber composition. The food product is produced by a process involving extruding the dietary composition and at least one food ingredient and water to produce the food product; the dietary composition produced by a process involving extruding a protein containing product and water through an extruder to produce the dietary composition, wherein the dietary composition contains partially denatured protein containing product or totally denatured protein containing product or mixtures thereof.