Studies suggest that dietary fiber from whole grains such as wheat and oats increases stool weight.31 The increase in stool weight is caused by the presence of fiber, water that the fiber holds, and partial fermentation of fiber and oligosaccharides, which increases the amount of beneficial bacteria in stool.32 The large intestine responds to the larger and
softer mass of residue
produced by a higher fiber diet by contracting, which speeds the movement of the
bowel contents towards excretion.