Fat Boy

HFLC and Atkins will give you trouble on anything over an endurance pace. Once adapted, you'll be able to go forever without eating, but you definitely won't have any snap to your legs for anything tempo or above.

Paleo/Primal diets are independent of macro splits. Yes, you are eating meats and no you aren't eating grains, so it tends toward the lower end of the carb spectrum, but you can split it about any way you want. For overall health, I think heading in this direction on eating is a smart idea. You would have to be smart on your carb supply, but I really don't think these diets limit you to the extent that they should necessarily hurt your performance.