14 year old starting to run!!!?

First of all, good for you in taking it upon yourself to get healthier. As far as diet you need to create a different lifestyle basically. Stay away from fat and sugar and make a habit of thinking about healthy food whenever you think about eating. I'll attach a link or two about getting started in this. When you head out to begin your first run don't push yourself too much. You want to get an idea of how far you can go and what pace you can keep. Stretch thoroughly so you don't injure yourself. Start with 2 kilometers, see how you feel. Get your muscles, lungs, and heart acclimated to running before you really start pushing your limits. End your run with a long cool down.