Martial art does not bulk you up and while it will help you get more fit than doing nothing martial arts are about skill. You do have to be physically fit to be effective, but it is not the focus of any martial art to build bulky muscles. Furthermore, a serious martial artist do supplement training and not just go with what is taught in class. This means doing your own research on not only what kinds of exercises, but also how to do them properly AND also about good nutrition.

If you expect an instructor to teach you all that, you are going to be disappointed.

While doing martial arts or any exercise for that matter will tone you it will definitely not bulk you. For that you will have to do supplemental weight lifting. Too much bulk though in martial arts will not benefit you. Martial arts requires speed and agility which comes through good techniques not strength. Too much bulk will impair this ability and then you end up muscling everything. That's ugly and shows little skill.

I kinda have to agree with Tanner. If you want skills then go train Martial Arts. A lot of Martial Artists weight lift too. But if you want size first go start lifting

Weightlifting is the most efficient way to build muscle. As far as self defense goes, a gun is a much better choice.

Hey guys, I am a twenty year old college student and I am planning on taking up a martial arts. I wanted one that will get me fit but the thing is im not trying to lose weight or anything. I'm just very skinny and was looking for something that will bulk me up. This will be my first martial arts and I was thinking something like Taekwondo or Muay Thai. What do you recommend?

Thanks.