I've had a serious case of brain fog for ages and I've been told that it's likely related to my blood glucose being too high. I've been on the LCHF diet for a couple of weeks and my blood glucose in now in an acceptable range (most readings normal, although waking one typically around 6). I'm exercising - 5 hours a week of swimming. I'm just curious, those who had brain fog, how long did it take for it to go? It's so long since I remember thinking clearly that I can't even remember what it feels like! Maybe it's just me? LOL