The bulk of calories burned is determined by your resting metabolic rate, which is largely a function of how much muscle you have. If you think you'll just bump up your cardio for a while to lose weight, think again. You must add activities that burn calories, promote or maintain muscle mass and elevate your metabolism. It's not about adding more walking, treadmill, running or bicycling. It's about adding weight training. Muscle is an active tissue that requires calories to maintain, and muscle burns calories when it is working.
There are various ways to burn more calories when you exercise, including explosive exercise training, interval or circuit training, supersets, sprints, etc, some of which you may have heard of. Depending on whether you've performed a few minutes of light exercise or an hour of hard intervals, you'll burn calories hours after you've completed your workout - up to 38 hours, research suggests.