Best Martial Art for Slender Young Woman?

I'm interested in taking up martial arts - both for energy release and also for self defense (and exercise!). The only thing is that I'm slender - I weigh 55 kilos and am 5 ft 5 in.



I'd like to be realistic about this - what would be the best martial art for someone like me? And what are my main options?



I've looked at karate and am tempted by this.



Any thoughts? Thanks