I think it's a mix of genes, stress, and other lifestyle stuff. Like, hair loss is in part genetic and in part stress-induced, and when guys start getting male-pattern baldness they start looking older. Wrinkles are in part inevitable and in part caused by sun exposure, smoking and stress. They make people look older. Yellow teeth from coffee and cigarettes make people look older. Gray hair is part genes and part stress - and it makes people look older. A beer gut makes people look older.
To use me as an example, I don't smoke or drink, I try to avoid unhealthy stress, I don't fake-and-bake, I'm thin and still have the same hair-line I did when I was 17 and the same waist-line I had when I was 14 (seriously, I'm not shitting you on that one - I still have clothes from back then). People routinely mistake me for being around 20 - 23. I find it flattering most of the time, but frustrating when it means I'm not taken seriously. Meanwhile, younger friends of mine who have lived hard look way older than I do. C'est la vie.
To use me as an example, I don't smoke or drink, I try to avoid unhealthy stress, I don't fake-and-bake, I'm thin and still have the same hair-line I did when I was 17 and the same waist-line I had when I was 14 (seriously, I'm not shitting you on that one - I still have clothes from back then). People routinely mistake me for being around 20 - 23. I find it flattering most of the time, but frustrating when it means I'm not taken seriously. Meanwhile, younger friends of mine who have lived hard look way older than I do. C'est la vie.