I noticed that my food (and energy) intake is higher when I consume Artificial Sweeteners (except for sucralose-"Splenda"). Why? because it's stimulating appetite! Really!
Anyway, about the carb question. Eating too many carbs after a long low-carb diet is pretty bad. Yes, low carb, high protein and fat diets can impair insulin sensitivity and glucose tolerance. Your insulin levels will jump to the sky and fat gain may occur, especially in the presence of FFA (which further causes insulin resistance).
I remember JB wrote how to come off from a ketogenic, low carb diet without gaining too much fat and water.
Here is the link:http://www.t-nation.com/readTopic.do?id=461792