Martial Arts? Boxing? Wrestling Alligators?

I box and kickbox and will be starting Krav Maga in a few months. I HIGHLY recommend it. Look up a few clubs in your area, pick a class, and get to work.

You'll need to build endurance, so my recommendation with that is skipping. Grab a rope, learn to skip like boxers (youtube, etc), then do it. It will be brutal at first, but you'll see improvement fast.

Also, make sure you watch your protein intake; you'll need MUCH more than you're getting. I believe it's 1g of protein per whatever weight you want to be, so 160g or more for you. You don't want to lose the muscle you'll be building!!

You'll also need good carbs before your workout, since it will be intense. I make oatmeal in the morning with two scoops of protein powder, some almond milk, and a bit of honey and cinnamon. Make sure you also eat the majority of your exercise calories back -- your body needs the fuel.

Give it a shot and don't give up! Chances are, you'll love it.