30 Day Shred isn't some kind of miracle weight-loss tool. I did it once, all 3 levels, and I got stronger and was able to do more reps of heavier weight after a while, but I don't think I lost too much weight (I can't remember).
Weight-loss is 80% diet, 20% exercise. The video is great and you will definitely feel stronger and more fit afterwards, but don't expect it to be a cure-all! Just stay active, eat well, and do the video if that's what you're in the mood for! (Oh, man, level 3 is a killer!)