****Warning this is a Rant with real sound medical advice****
If you want to jump start your diet, and exercise program, and feel this will help by all means go ahead, but be warned.....
Your body has it's own natural way of cleansing itself. It's called going to the bathroom. Your liver, and you kidneys, your lymph system, and your blood all play a part in filtering out the crap. If you feel yucky because you have been eating crap, that's because it's more than your body can filter out efficiently.
I would suggest eating a very clean, diet for 3 days instead, and see how you feel. Probably much better. This means NO PROCESSED FOODs. Fresh fruits/veggies, at least 5 servings of each daily. Lots of good lean proteins, fish, chicken, nuts, seeds, and beans.
HERE IS THE WARNING PART OF THE CLEANSE - When you do this you dehydrate your body, and depending on your tolerance, and what you are drinking you can cause minor things from headaches, to feeling sickly to significant things like Atrial fibrillation (irregular heart beat) and Renal failure, yes Kidney failure.
I have seen it happen in people in their late teens and 20's, I have seen it happen to people in their middle age. So my word of warning is a simple 3-7 day cleanse can turn into an all inclusive stay at your nearest hospital. Where the staff will be more than happy to poke you with needles, and the hospital itself will be more than happy to charge you or your insurance crazy sums of money to get you back to healthy.
Thus Ends my rant.