Fructooligosaccharies (FOS) also sometimes called oligofructose or oligofructan, is a class of oligosaccharides used as an artificial or alternative sweetener. FOS use emerged in the 1980s in response to consumer demand for healthier and calorie-reduced foods. The term oligosaccharide refers to a short chain of sugar molecules (in the case of FOS, fructose molecules). Oligo means few, and saccharide means sugar.