RTMNF - yes, one data point certainly means nothing.
My wife says the comparable brands in the USA might be as follows (we are both expats):
Pennington's - plus size, women's only, like you said, it's not casual wear, perhaps best comparison is Torrid except the stores are bigger and Torrid is mall-based (walked by Torrid yesterday too and there were a decent amount of folks in it).
Reitmans - women's only, in terms of type of clothes they carry, the best comparisons are Suzy Shier and possibly Express (except Express sells men's clothing too). For both our sakes, let's hope Express isn't an exact comparison lol. I do think that the reputation is better than Express' in Canada and they are often present in many smaller cities/towns.
RW&CO - she wasn't familiar enough to make a comparison and I've never been to one of the stores.
And yes, I was kind of stunned to read some of those articles about weight gain. Perhaps WW is the play :P? Always remember, Canadians are skinnier than Americans, but there's certainly obesity problems up here too.