I don't know the "official" answer. In three years of Adam's Diet questions, this is the first time I've been sorta stumped.
Here's my take. I read several study abstracts and articles based on studies, where Atkin's Advantage bars were tested against other bars for their effect on blood sugar. These bars won, hands down. The least likely to increase blood sugar levels. Even over the ones with the sugar alcohols. So...
I just found the ingredients listed online, and there's nothing all that bad in them, either.
Therefore, I'd eat them (I had one on Monday, in fact
) in moderation. The biggest downside for me, is that they don't actually fill me up or satifisfy me, so I crave another one, immediately. I didn't have another, so I was merely miserable.
The one that I had had more like 250 calories, I think. Maybe they have different sizes.
If eating one of these is convenient and you continue to see progress, then I'd eat them in moderation. If you see a stall or feel that they might be a trigger to bad eating behavior, then look at ditching them.