In order to burn fat through exercise you have to do a lot of work in a short amount of time. Walking, jogging and other long slow forms of cardio are only effective for a very short period of time because your body will adapt to it very quickly. Basically your body will be able to move more efficiently and burn less fat so even though you will get better, you won't be burning more fat! It is cruel I know, but there is a way to burn effectively through exercise over the long haul, you just have to be creative.
Circuit training is probably the best method for fat loss because it can be done anywhere with anything, even your own body weight! The key to circuit training is to pick a series of exercises you can do in a row without waiting. For example, if you are in the gym grab a light pair of dumbbells, a flat bench and a mat and do 15 reps of the following exercises:
stiff legged deadlift
step-ups on to the bench
Once you have done one set of roughly 15 reps for each exercise repeat the circuit starting at the first exercise again. Keep moving for about 20 to 45 minutes. If you can't do 15 reps of one exercise, just do as many as you can and move on to the next. The key is to keep moving your body and those dumbbells. This will be a challenging workout but it will burn so many calories and tone up your muscles so quickly that I guarantee you the work will be worth the reward! For more ideas, check out this video below!