Hey. It may not be the Atkins bars. I don't eat them and I have had diarrhea as well. I am on day 9 and had it from day 2 until day 7 and now am quite regular. I was doing the BFL way of eating and was constantly constipated with the occasional good one! LOL So it's great now that I had diarrhea as it was a kind o a clean out and now things are 'normal'. I think it's just the exra fats in the diet that we are not used to. Everybody is different in the way he handle food in our diets.