Bodybuilders have been doing slow-and-steady cardio for decades in order to drop bodyfat while maintaining muscle.
A boatload of research shows that doing high-intensity interval training, such as sprinting and resting, works much better to burn off bodyfat.
University of Western Ontario (London, Ontario) researchers had male and female subjects follow a six-week cardio program. One group did slow-and-steady cardio for 30–60 minutes a day, three times per week. The other group only did four to six 30-second sprints with four minutes of rest between sprints three times per week (a total of just 2–3 minutes of total cardio per workout).
The subjects doing the sprints lost more than twice as much bodyfat as the slow-and-steady cardio group.
Sprinting for only 6–9 minutes per week doubled the amount of fat subjects burned off compared to those who were doing slow-and-steady cardio for 90–180 minutes per week. The slow-and-steady group did up to 30 times more exercise per week, but only lost half the amount of bodyfat. Sprinting is the clear winner due to the better results and the reduced amount of time you need to devote to it.
Find an area that gives you enough distance to sprint as fast as you can for 30 seconds straight. Do six sets of sprints with 1–4 minutes of rest between sprints. And feel free to do more than six for even greater fast loss.