Stretch marks can occur in both sexes at any age and are certainly not solely associated with pregnancy. They can occur with a sudden change in weight or even in children after a spurt of rapid growth. When the skin has to stretch for any reason the connective tissue has to be elastic enough to allow the movement of one layer of skin on the other. If the connective tissue tension is tight the tissue tears instead of stretching rather like an old elastic band.
Stretch marks are often hereditary but can be prevented by Connective Tissue Manipulation, which ensures that the connective tissue in the skin is elastic enough to enable it to stretch without tearing.