If you are on Atkins Induction, then chocolate is not on the acceptable foods list. You could be sabataging yourself, especially with a bar a day. That is a significant amount. Carbs or no carbs, some foods can trigger cravings or an insulin release. It could be triggering cravings - you mentioned you fell off the wagon on the weekend - I would suggest doing a "clean" induction to kill your cravings and reset your body. Then perhaps later you can try adding in the chocolate and see how your body and weightloss responds.