From the Wikipedia entry: #Yacon is a species of perennial #daisy traditionally grown in the northern and central Andes from Colombia to northern Argentina for its crisp, sweet-tasting, tuberous roots.
The edible storage tubers are large and typically weigh from a few hundred grams to a kilogram or so. The tubers contain fructooligosaccharide, an indigestible polysaccharide made up of fructose. Fructooligosaccharides taste sweet, but pass through the human digestive tract unmetabolised, hence have very little caloric value. Moreover, fructooligosaccharides have a prebiotic effect, meaning they are used by beneficial bacteria that enhance colon health and aid digestion.