Proper butter squeezes all the whey white stuff out. Clarifying the butter squeezes out more. I did check the caloriecount database, a cup of heavy cream has about 6.5 grams carbs and supposedly no sugar. Don't know if that's enough to make a difference.
But yeah, the calories are an issue too.
5'0" female, 43 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Current weight: skinny-fat 106.5 lbs because of sugar cheating.
MY PRIMAL: I (try to) follow by-the-book primal as advocated by Mark Sisson, except for whey powder and a bit of cream. I aim for 80-90 g carb/day and advocate a two-month strict adjustment for newbies. But everybody is different and other need to tweak Primal to their own needs.
Don't be scared of fats. I eat 250 grams of butter a day, along with lots of gouda and other dairy fats and have been doing so for quite a long time. My bloodwork was good too. I only eat carbs in the form of green vegetables and occasionally munch potatoes, rice and sweet potatoes for it's anabolic effect on the weekends.
I know I am not huge, but I am bouncing back from evil illnesses and there has been no fat gain during my weight increase.