At first, I found it challenging yet still fun. I managed to still keep up and I couldn't wait to continue. Eventually I got addicted. I was doing three workouts a day cuz I couldn't stop... The only reason why I would stop was either for work or bedtime...and my bf would have to pull the plug. I was outdoing most of the ppl in the program by pushing myself harder and not taking beaks at all, just doing plyo jumps or pushups during water breaks and starting the next vid right away, and others have witnessed it too in astonishment. I did this for almost a year, and was obviously underweight. I never followed the nutrition program either, just tried to stay low calorie and low carb. I was also doing p90x at the same time. Yup I had a problem because my whole mindset used to be just on working out, even at the sacrifice of my health.