The bars (and candies) have sugar alchohols in them so if you are one of the people who's bodies metabolizes them - and does not ignore them - and you eat a bar that states 3 NET carbs with 27 sugar alchohols your body treats it as though you just ate 30 carbs.

Also, if our body is sensitive to sugar and eating a tiny amount starts cravings for more sugary things then the sugar alchohlos in the bars can have the same effect. Trust me I was addicted to the bars and candies and had to go cold turkey.