INSANITY workouts

I'm looking for any and all advice or encouragement from those who are doing or have done the INSANITY 60 Day Challenge.

I'd also like to know what percentage of carbs you take in during INSANITY. I know they recommend 40%, which will be really hard for me to hit because I'm on a grain-free diet. I know how to get my carbs up if I absolutely have to, but I'm interested to know if anyone has had success on a lower carb diet? I naturally eat a high protein, high fat diet.

I will be starting INSANITY next week when it arrives in the mail. I am not overweight because I eat healthy, but I'm definitely not in shape. The last time I exercised regularly was over 10 years ago. This is going to be interesting!