For the next 22 days while you are upgrading your metabolism from a sugar burner to a fat burner, walking is the exercise Dr. Jonny recommends.
Dr. Jonny believes that the reason it's so hard for people to lose fat by exercise alone is because they are sugar burners. Sugar burners tend to run out of steam pretty quickly since they can't effectively tap into their fat stores for energy. Often they'll get exhausted because the endless supply of energy they've got locked up in their fat tissue isn't available to their cells for fuel.
In the 22 days that you do the Metabolic Factor program, you're upgrading your body to become a fat burner, making sure that the fat stored in your body is available for your cells to use as fuel.
Walking is not too demanding on your body and it conditions your body to improve endurance, improve blood flow and improve your fat burning without increasing your cortisol levels.
Then, after the program, when you decide to increase the intensity of your exercise and consider a rigorous fat blasting program like High-Intensity Training, your metabolic engines will already be primed.
You can refer to Chapter 11 on the Metabolic Factor Blueprint for more detailed discussion about exercise and the science behind walking as a recommended exercise for the 22 day program.