Think about it: Week 4

Intensity of Cardiovascular Exercise for Weight Loss

There is a myth that in order to burn fat, one must train at low intensity for a long duration. It is true that a greater percentage of the calories burnt during low intensity exercise come from fat compared to high intensity workout. However, you have to remember that if you are working out at a low intensity your TOTAL amount of calories will be lower compared to a high intensity workout.

This means that if you walked for 30 minutes, you simply would not burn as much fat as if you had jogged for 30 minutes - even if fat burning is more efficient when you are walking. This is because you burnt vastly more calories when jogging that despite the fact that it wasn't as efficient as walking at burning fat, you still burnt more "fat calories".

Example,
Walk/low intensity/burn 100 cal of which 75% cal from fat = 75 fat calories
Jog/high intensity/burn 250 cals of which 50% cal from fat = 125 fat calories

For sustained weight loss, you have to burn more calories then you take in. Therefore, trying to focus on burning fat calories won't help. Calories are calories - the goal is to burn as many as possible. Thus, to burn as many calories from fat as possible you should perform longer durations exercises at a moderate to high intensity. Basically step the intensity up to as high a level you are able to sustain for 30-60 minutes; this is your "training zone". Generally, this tends to be 65-80% of your maximum heart rate.

If you are already doing cardio, DO IT HARDER, increase your intensity and advance closer to your fitness goals.