Martial arts are currently studied worldwide from a variety of cultures. Martial arts can improve your fitness levels and muscular condition immensely. Depending on the martial art you choose to do, you may even learn some effective self-defense techniques.
There is a major debate as to whether martial arts are effective as self-defense. My personal experience has taught me it is best to study as many styles as you can and question what works.
What I have done is take techniques, which I find work from a few styles and then design a fighting system and practice based on me.
To simplify the above choose the best techniques from each style and use them in your own practice. This probably goes against the culture of martial arts, however for self-defense you cannot possibly expect to be held down to a set form. That is like a brick in water. Think if you are on the street, do you honestly think you are going to have time to pull of a full-blown technique and fancy kicks? I don't think so. That's why it is best to be open to all techniques and styles.
Studying martial arts for me is not even about self-defense. If I wanted self defense I would learn to be a street fighter. It is more about developing my body to its full potential. By this I mean getting as physically fit as I can. Not only is there the fitness aspect, there is very deep meaning to the martial arts. It is a way to express your self through movements. This is why I personally see it as an art. The martial arts are an honest form of exercise and discipline. They can help you in your weight lifting, as after a while you become more aware and feel a strong spirit within. This can help in any exercise program.