Dietary fiber is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes.

Dietary fibers are diverse in chemical composition, and can be grouped generally by their solubility, viscosity, and fermentability.

Soluble (or prebiotic, reduce blood sugar spikes) and insoluble (inert, a bulking agent) fibers are components of plant foods, which  contain both types of fiber in varying amounts.

Fermentable fibers (resistant starch, inulin, pectins, beta-glucans, guar gum, oligofructose) feed the microbiota of the large intestine, and are metabolized to yield short-chain fatty acids. The best source is legumes.

Bulking fibers (cellulose, hemicellulose, psyllium) absorb and hold water.

Viscous soluble fibers like (beta-glucan, glucomannan, pectins, guar gum, psyllium) fibers form a thick gel when they blend with water, slow down the digestion and absorption of nutrients, reduce appetite. They are found in peas and beans, asparagus, oats, and flax.

Resistant starch improves digestion, enhances insulin sensitivity, lowers blood sugar, significantly reduces appetite, and found in legumes, green bananas, cashews, cooled down potatoes (or raw) and rice.

Fructans, polymers of fructose molecules (oligofructose, inulin) are found mostly in agave, artichokes, asparagus, leeks, garlic, onions, grass, and wheat, and are not suitable for all.