I say you have to find out what works for you. Marks book isn't a fit all, it's a guide and is mostly beneficial to those dreadfully overweight people who have developed a bad relationship with food.
Food is not the enemy.
I have the odd cheat day, and I know a lot of others who do, it's sad to see people paralysed by a purist attitude who daren't eat anything off menu and then obsess constantly about food, how is that healthy?
I would suggest try it, you may find like many people do that your body revolts and you feel like crap afterwards and it was no where near as fun as you thought. You may find that as part of your programme it keeps you psychologically happier, do what works for you.
Perseverance is not a long race; it is many short races one after the other.
I am a horse for a single harness, not cut out for tandem or teamwork; for well I know that in order to attain any definite goal, it is imperative that one person do the thinking and the commanding. Albert Einstein