There are two types of ageing of the skin which leads to loose or lax skin: "true" ageing due to chronological age and "photo" ageing, due to the toxic effects of cumulative sun exposure or other environmental toxins, such as smoking, pollution, and lack of circulating antioxidants (diet).
The two types of ageing manifest themselves in slightly different ways. In true ageing, the skin produces less collagen and elastin and the fibril layers loosen and become less organised. This causes the skin to sag and become thinner resulting in the classic signs of ageing. This process is accelerated by sun exposure or photo ageing making the skin older before its time. Another cause of loose body skin is having one or more children or sudden weight loss.