Understanding Double Chin Concerns A “double chin” usually refers to fullness beneath the chin, also known as submental fullness. This area can affect how the lower face, jawline, and neck appear from the front and side. For some people, fullness beneath the chin may make the jawline look less defined, even when their overall weight is stable. Double chin concerns can be influenced by several factors, including genetics, aging, weight changes, skin elasticity, and natural fac