How often is too often to take a laxative to aid in weight loss?

I have seen and heard alot about the colon cleanse products. I have a few friends who use them every week. I am worried that is too often. From a medical perspective how often can it be done without negatively impacting your health. I currently do 15 minutes of cardio and 45 minutes of weight liftiing Mon. thru Fri. I am committed to continuing my regiment of portion control eating and working out, but if it can be done responsibly...I'm game.