Will gravity alone change your face if your facial tissue didn't 'age'?

I hear it said a lot - when reading about the ageing process and plastic surgery - that gravity will cause things like the philtrum to lengthen, or face to get saggy, etc. So what I'm wondering is, when they say this, do they mean to say that as a result of poorer quality skin (with less collagen, etc) that gravity now has more of an effect, OR, that gravity will effect every over time even if their metabolic age remains the same for ever? which I presume is all down to the efficiency of your genes.

Thanks