This is that age old myth that you must do a half hour to an hour of that stuff they call cardio. Not only is this a waste of time but it hardly yields a significant calorie burn (don’t even try to give me the old, “it burns more fat calories”! That is BS and a half truth). If you want to rip the fat off, you are going to have to kick the intensity up and work! Try to incorporate some interval training sessions in your week. Start with a 30 second sprint and 1:30 rest. Repeat it 4-5 times. Not only will you burn more calories in a 15 minute session of intervals than you would in 60 minutes of steady state aerobics, but you will continue to burn calories throughout the day! This is due to EPOC (excess post oxygen consumption), or what Alwyn Cosgrove calls "The Afterburn". Try keeping your work the same (30 sec) and shorten the rest periods over the weeks. Save that boring half hour stuff for your recovery days. And oh yeah........its called "energy system training", not "cardio".