I can honestly tell you i was a slug. I was always an athlete in my younger years and worked out frequently as i got older, but once i hit 40, I pretty much stopped doing that, and ate everything i could put my hands on. I'm 6'1" and was 240. Not obese, but I definitely felt like 10 pounds of in a 5 pound sack. My goal is to lose 25 pounds.
Started insanity with some coworkers. We get up 5 days a week and do it at 6:30 AM. It's hard work for sure. I can tell you that after the first month, I lost 10 pounds, but diet is KEY as well. Eat small meals no larger than your fist (the size of your stomach) and eat HEALTHY. egg whites, chicken breasts, multi grain bread, tomatoes, veggies, healthy fruits, fish, lower on salt if possible, etc. They give you a diet book, but I swear it's a full time job to organize your eating 6 times a day 7 days a week.
As for the workout, we are repeating the first month (like starting from scratch) and I still can't get thru the entire workout at THEIR pace, BUT... the people in the videos are all 20-somethings in FANTASTIC shape. It's no surprise I can't keep up. Still, doing the best i can. It's DEFINITELY easier doing it WITH people. They help hold you accountable and push me more than I would myself. Just my $.02. I really like it tho. Bought it on e-bay for about $80 and got the original everything for it. Didn't go to their website (I think it's like $120 at their website)...