Try running 30 minutes varying your intensity you may find some very good results. Generally 2 mins. easy jog. Then 2 mins faster. Then 2 mins close to a sprint almost. Then repeat the cycle. Your causing your body to adapt to the increased intensity therefore making it rely on more energy to support this. Mix it up try steady jogs one day then vary your intensity the next. Besides it takes away the monotony of everyday cardio.