I dont know about these kits, but I did the master cleanse that someone else mentioned. I did it for the recommended 10 days and I was happy with the results. I felt great during and after. I wish I had kept to better diet after, I want to do it again sometime.

I think you're metabolism is slowing down due to years of excessive calorie restriction. 900/day is too little for an active 18 year old. I think you'll have to increase you calorie intake to get your metabolism going again.