Yruam, this is one of those YMMV issues - your milage may vary. The 'impact' carbs they discuss on "LC" bars are usually sugar alcohols and glycerine - not fiber, as with whole foods. Sugar alcohols and glycerine can actually cause problems for many - some diabetics experience an insulin spike from them. Your best bet is to try them and see for yourself. If you start to stall out, or you losses slow and /or you start to experience cravings then you know that they're a problem for you. If not, then more power to you.

HTH
Nat