"Insoluble fiber" refers to a type of dietary fiber that does not dissolve in water. It adds bulk to your diet and helps with digestion by promoting regular bowel movements. Full definition
Often this could be something such as a lack of insoluble fibre in the diet, which is fairly easily remedied. (colonzone.org)
Nuts are particularly high in insoluble fibre which has zero effect on blood sugar. (KetoDietApp.com)
Short chain fatty acids (SCFAs), which include acetate, propionate, and butyrate, are produced by bacteria in the gut during fermentation of insoluble fibre from dietary plant matter. (sciencedaily.com)