Personally I wouldn't worry about it for now.
Read the book, get to grips with the nutrition side of things. In a few weeks or a few months time you'll most likely feel a hell of a lot better than you do now, and moving your body will start to become something you actually want to do rather than something you feel you should do. If you start exercising because you want to, you're way more likely to stick with it.
You don't need to exercise to start losing weight. Yes, it'll help and in the long run I'd say it is essential but why not walk before you can run (pardon the pun).