1 The dermis of the skin with protein loss contains collagen and elastin, which supports the skin to make it full and firm. But after the age of 25, these two kinds of protein naturally decrease due to the aging process of human body, and the fibers between cells deteriorate with time, making the skin lose elasticity.

2 Decreased skin support Fat and muscle are the biggest supporting forces of the skin. The subcutaneous fat loss and muscle relaxation caused by various reasons such as aging, weight loss, unbalanced nutrition and lack of exercise make the skin droop without support, which is also the main reason for skin relaxation.

3 Decline of skin metabolism Our skin actually has its own metabolic function, which can decompose aging damaged collagen and elastin, and at the same time, it can also make new collagen and elastin to replace it, thus maintaining the richness and elasticity of the skin itself. However, the speed of these metabolism will gradually slow down with the aging of cells; The old can't be decomposed, and the new can't be made, which leads to the fragility, looseness and inelasticity of the dermis.

4 Excessive weight loss Excessive weight loss or rapid fat loss in a short period of time will lead to sagging skin, or it may be due to lack of water, firmness and elasticity, and it is easy to rebound after losing weight.