We recommend that you stick to working ou three times a week for the 12 weeks required to finish the program. The one exception here is if you are a menstruating woman in the luteal phase of your cycle. During this phase you can add one more workout and eat a little more. All of the details for this are in the book.
For days off, movement instead of workouts is highly recommended (See What do I do on my days off?).
Workouts should not be done every day because recovery is just as important as the workout itself. But it is important to move as much as possible every day, so feel free to add walking, gentle swimming, relaxed cycling, yoga, stretching or other forms of movement that don’t strain your body.
It is not recommended to do full workouts such as group cardio classes or weight lifting in addition to the metabolic workout. Relax, and look to your days off as time for your body to recover.
Please be sure to stick with the program as it’s designed but know that there is a strong likelihood that you will be more challenged as the program progresses.