I read where alot of people (mostly women after there pregnancy or great weight loss, so I would guess it would work for a guy) had success in using an exfoliant like Dr. D suggested, but also using copper-peptide bonds also. Dr Loren Pickart found these copper peptide bonds. He says the exfoliant will do what Dr. D says, then the copper peptide bonds will repair the skin deep down.This guy sells copper peptide bonds for hair loss, and Will Brink recommends them for that.
Heres his link, look thru page and you'll see a link to help with stretch marks and sagging skin (as well as sun damaged skin, hair loss etc)
Skin Biology