Forgive me if i'm not understanding this, are you saying the advantage of 5-6 smaller meals is that people tend to overeat when eating less frequently and overall caloric intake is higher for those eating less often? if that is the case then yes I will agree with you. That said, if macros are tracked effectively then there will be no advantage.
and yes, its safe to assume the average American ingests enough fat but one of the first things people eliminate when eating "healthy" is sat fats or even fats in general. and I agree, protein shakes are fine and I actually just consider them food rather than a supplement.
As far as GL, GI, and their effect on insulin are concerned insulin's role as a fat storage hormone is far overblown and can't overcome a caloric deficit.
http://articles.elitefts.com/trainin...claims-part-1/