When you start to practice, you start to do a lot of exercise that is good for your body and is good for your health. Here are some things that you start to develop thanks to martial arts:

Balance: Your body balance it increase, it really does. In classes you will learn to have a good balance to do some kicks or some positions, and then you start to notice that you can do activities in your daily life without lose the balance of your body.
Strenght: You become stronger because of the physical work that you do. At the beginning you will feel that you are terrible in those things, but is okay, because is not usual to do the exercises that we do in karate. After to practice for a while you realize that you can do heavy lifting easily, and is really useful in daily life.
Elongation: You must to do a lot of elongation, in that way you can do better kicks. This is one of the most signitficative changes, because you compare how was your elongation when you start to practice and how is after. Is really satisfactory to see it.
Of course that to do all this changes in your body, you have to be constant and put all your effort in it!!!