All you need is an extra 15 minutes a day for HIIT cardio (high intensity interval training). Doing 45 minutes of cardio is going to not only burn off fat, but it will burn off your muscle as well. HIIT is the best way to burn off that fat quickly and retain your muscle. Read about it and trust me, you will feel more drained after a 15 minute HIIT session than if you did a 45 minute regular cardio session

You will have to start off slow, but there are charts on how to start out included on the page. They will kick your ass until you get in shape enough to do the full 15 minutes.
There are a ton of pages on HIIT, but here is a simple one for a beginner:
http://www.musclemedia.com/training/hiit.asp
Good luck to you!