Urine fasting is a safe way to loose weight, but when you return to eat again, is very important to watch what you eat. You have to eat little by little, and don't go back to your normal eating habit.
One good way to do it is to eat raw fresh vegetables and fruits the same number of day that you fasted.
And in order to diminish the detox simptoms it's important that you eat also raw fresh fruits and vegetables some days before starting.
I think it's very important to prepare also mentally for the fast.