Well, first of all, if you are significantly overweight or have health issues, then you absolutely need to consult with a physician before you undertake anything even approaching this extreme. In fact, it's never a bad idea to talk to your doctor before doing anything like this even if you don't have any particular health concerns.
Another thing you need to take into consideration is whether you have the strength of will to undertake the project. If you do choose to undergo the detox fast, know that it's not going to be easy. Results that intense obviously aren't going to come easy, or else they would be easily achievable by anyone with the inclination. Of course that's not the case.
Also, if you are going to decide to undertake this project, make sure you get the highest quality ingredients. You can't do this with Countrytime lemonade and regular old maple syrup like you'd put on pancakes.
Since these ingredients are going to be your sole source of sustenance, and the point of this is to detoxify your system, you need to limit what's going into your body to the very best quality to make the cleanse as effective for detox as possible.
To find out more about the Master Cleanse detox diet, including constantly updated tips and resources, go to http://master-cleanse-detox.blogspot.com