hi suggest you hold of the exercise until you have completed 2-3 weeks on CD. Then doing a little at a time. I found I was lighted headed and felt tired in the first 2 weeks - withdrawl from carbs, caffeine etc. and also very low calories. By week 3 I started at the gym and then increased my sessions upto one hour. I have to say I was a couch potato when I started. I am now on 810 though. See what others have to say.