I did the 30 day challenge from simplegreensmoothies. It was the most fantastic thing I have done for my body! Granted... I am not doing it at the moment. I got thrown off by closing on a house - but as soon as we move in and get settled I had sworn to myself I will start up again. My mother actually convinced me to start (tomorrow) by pre-prepping our smoothie ingredients in the freezer.
While I was doing the 30 day challenge I found recipes I loved... and hated. Some days I lost weight, others I maintained, a few I gained. Overall my health and energy felt significantly improved! I felt so great in my body! My skin was clearer, my mood was happier, my stomach wasn't upset all the time, I was very content and had LOADS of energy!
If you go this route I would suggest signing up for the 30 day free challenge and then pre-prepping your smoothies by week in the freezer (ie. put all ingredients in a quart bag in the freezer EXCEPT the liquid - add that the day you make the smoothie). You could also just get all the ingredients set up the night before and mix it then and grab and go in the morning!
(Sorry to sound like an advertisement... I was just so thrilled with my results from it)