What Exactly Does Kybella Do? Kybella is an FDA-approved injectable treatment designed to reduce fat cells in targeted areas, most commonly the submental area, which is the space under your chin. The active ingredient in Kybella is deoxycholic acid, a naturally occurring molecule in the body that helps break down and absorb dietary fat. When injected into the fat beneath the chin, Kybella destroys fat cells. Once these cells are destroyed, they cannot store or accumulate fat