Although I'd imagine a liquid diet where you are mainly only consuming smoothie type beverages has to be less hard on your digestive system just because of the simply fact it requires less effort to break down?
If you want to have a healthy body you have to put it under a stress level for which it was designed by evolution. I.e. exercise once in a while and don't just sit in front of your computer, eat enough fibres and harder to digest food, etc