Very common. My girlfriend who is the same age as I am, but 20 pounds lighter has incredible wrinkles. Of course, it's also genetic and sun exposure to a degree.

Aging is rough on your looks, fat, thin, whatever.

I do think if you are trying too hard to be thin or if you are obviously too thin (Demi Moore currently, Courtney Cox a few years ago) it makes you look older. But extra weight makes you look older too. Extra weight or not enough weight is more easily handled/looks better on a younger person, just like everything. Most things having to do with your physical self are easier to pull off in youth. Just be healthy and age gracefully. Beats plastic surgery!