Perhaps it is not supposed to, but for me it does. Whether it is up or down, the first few times a size does not fit, I figure that it is the brand, but then when it happens with several brands I think that I am either really gaining or really losing the weight.
I notice that for most clothing, for those sold in the US it is a made about full size larger that it is in Canada. I now wear a 6 for most items in Canada and I find this is usually a 4 in the US. (juniors are totally different in the gap though). I have to admit the elation that came with the very first comfortably fit size 4 garment