Loss of volume refers to the natural reduction of fat, collagen, and other supportive tissues in various areas of the face and body, leading to a more sunken or hollow appearance. As we age, the body's production of collagen, a protein that provides structure and elasticity to the skin, decreases. Additionally, fat cells that help maintain a youthful fullness begin to diminish, leading to a loss of volume in various areas of the body, including the face.