I am not one to disparage anyone else's methods-- I believe that if you're doing something you enjoy, and it is working for you, all is well. However, when it comes to Tracy Anderson and programs like hers, I have to speak out for the following reasons:
1) she is trying to push her unproven, nonsensical theories as some kind of science/fact
2) she is essentially pushing an extreme eating disorder(600 calories/day is an anorexic pattern)-- and making bank on it. Having grown up around eating disorders, let me just say this is not a game, and could turn deadly.
Do what works for you, but please remember that if it causes your health to decline, it is not working for you-- no matter how "small" you get.