Vanity and fitness could be somewhat synonymous - you need to be interested in the way you look if you are going to make the effort that more than 80% of the adult population will not do.
Health and wellbeing are side effects along with the mental boost and feeling of increased self esteem that follow a good fitness session.
Here is a great article recommended by Erika that illustrates the authors perspective on the link between fitness and vanity - a good dose of inspiration!
I found this article online and think it's a great one to share. It share my exact sentiments of well, being slightly vain, but overall being healthy and what exercise does for me.