If you want to do it fast, there's only one way: interval training. It's metabolically much more cost-effective than standard the steady-pace kind of cardio most people do (as well as conditioning you more realistically for the stop/start kind of rhythm that MA training seems to involve). The downside is, it's rather unpleasant. If, say, you run for twenty minutes, three times a week, using the formula 50 sec jog/10 sec full sprint for each of those 20 minutes, and combine that regime with a 250 calorie reduction in your intake, you'll easily lose between one and two lbs a week. Over three months, that'll be between 12 and 15 lbs. And your workout times will be shorter than with plain old jogging or whatever.
But as I say, intervals don't feel very good after the first few minutes. That 50 seconds seems to go by very quickly and the 10 second all-out sprint seems to take forever, and by the time you finish you are really wasted... no such thing as a free lunch, even a low-fat calorie reduced one... still, if you want reliable, steady weight loss pretty much guaranteed in a relatively short time, interval training is the way.