It might be worth looking at examples of people who don't seem to have aged a lot too. Jared Leto, for example, is a vegan who is chronologically 45 but looks closer to 28-32:
I think the genetic lottery is a huge, huge factor.
I myself am a fat fuck, have smoked 20-50 unfiltered cigs a day for over twenty years, hardly ever exercise and mainly eat junk.
At 40 there is a not a single line anywhere on my face or a grey or receding hair on my head. People I've grown up with who've led far cleaner lives could easily pass for a decade older than me.