DO NOT DO ATKINS AND INSANITY TOGETHER!!! Insanity has a nutrition guide geared specifically for it, and it's a 40% carb, 40% protein, 20% fat split for a reason.
You WILL get into glycogen depletion doing Insanity, and without carbs the only way to replenish those will be by breaking down your muscles for instant sugars.
If you want the results Insanity promises, follow the directions to a T, including exactly what the Elite Nutrition Guide outlines. That's what Beachbody does with the testgroups: feeds them exactly what the meal plan says, and lets the results speak for themselves.
Shoot me a message if you have any other questions about it. I've been through Insanity on its own twice, Asylum once, and 10 rounds of P90X. I might be able to help you get where you want to go.