Well, it's now no longer an issue. I'm a diabetic, and when I told my endo I was on Atkins, he flipped out. I'm on medication to prevent future kidney damage (which I already show the advanced symptoms of) and the high protein/fat content of Atkins is considered to be very bad for diabetics.

So I'm back to carbs at about 120 g/day as I was before, and my running is great now.

Thanks to all of your for responding!