Mainly three reasons they are,

1. After 30 minutes of anaerobic exercise you can continue burning additional calories for hours later since your metabolism continues to work at high levels for that additional time after the exercises. With aerobic exercise you stop burning calories once you finish the exercise.

2. If you do sufficient sets of anaerobic exercise your body will begin to heat up, your body will liberate lactic acid, and you will turn into totally breathless. These are three major aspects which support the natural release in your body of Human Growth Hormone. Human Growth Hormone causes liberated fatty acids to be released in your blood stream for burning and has frequently been referred to as the normal fountain of youth.

3. Anaerobic exercises build faster jerk muscle fibres. Fast jerk muscle fibres are denser than slow jerk muscle fibers and the faster jerk fibres you have the top your natural metabolism will be allowing you to burn an extreme top level of calories yet when you are doing not anything like sleeping.