A double chin, also known as submental fat, is a common condition that occurs when a layer of fat forms below your chin. A double chin is often associated with weight gain, but you don’t have to be overweight to have one. Genetics or looser skin resulting from aging may also cause a double chin.
When it sags it causes a wrinkle, which gives the illusion of having two chins. If the skin loses its elasticity it cannot hold the fat around the chin firmly. A double chin can also happen as you age and you begin to lose muscle.