This is always a difficult question to field, as there’s a lot of debate around the subject. It bears working through.
Lets assume that there are two main ways to do cardio work for fat-loss. The first is very light exercise, where the heart rate beats at around 105-120 beats per minute and there is little or no barrier to recovery. The second is highly intensive training, where your heart rate is pushed up close to its max, which functions to stimulate your metabolism and burn excess fuel.
Light exercise benefits from operating within the ‘fat burning zone’, meaning that proportionately you burn more calories from fat (though less calories overall) in comparison to other forms of exercise. A second benefit is that you can basically do as much of it as you like, as you don’t need time to recover from your exertions. Highly intensive training however, stimulates your metabolism to burn fat far quicker, but must be respected and given adequate recovery time.
With that all established, the crucial thing I find when working with clients is that a typical run manages to be neither one nor the other. The heart rate on a jog will not be optimal for fat loss, and the duration of the workout is often too long to benefit from the ‘in and out’ nature of intensive training. In fact, running can even bring about a negative change in your body composition. If you are not careful with your nutrition when running frequently, you run the risk of depleting your body’s glycogen stores, forcing your body to convert existing muscle into fuel for your workout. Consequently you lose muscle weight, leaving you with a higher proportion of fat in your body.
My answer to the question is that walking and sprinting are both excellent ways to burn fat. Leave the jogging for running events, not fat loss.