Well a lot of course depends on your fitness level when you start out. I had not worked out much beyond walking and bike for a year or more, then I started Daily Burn, True Beginer in Feb. It was a great bridge program for me because I had never done any sort of lunges or squats. Anyway, I began 30 day shred on March 26 after almost two months of that easier program. The shred was tough for me but it's doable. I was and still am pretty sore but stretching throughout the day helps. I found I needed a rest day on day 5 and day 11. I have finished 3 days of level 2 now and I feel stronger and definitely leaner.
I try to eat more protein such as hard boiled eggs, turkey breast or chicken when I first get up, wait and wait a few hours then do the shred.
I also get a burst of energy from doing the workout and a decrease in appetite for several hours after.