Did you know that you can faster and fitter by doing no training at all?
OK that's a bit far fetched but by dropping some weight resulting in less mass to move around then you'll automatically run faster, run further and be more injury resilient.
Dropping weight doesn't mean chicken, rice and water all day long either, it's a pretty simple equation - calories in versus calories out.
Depending on how hard you'd like to go with this, after 6 - 12 weeks you should be able to drop 3 - 7kgs through diet alone with minimal effort.
This manual gives you the precise breakdown of what macronutrients to eat, and how much.