haha i'm usually a "Top Model" only poster, but since i'm an avid watcher of all reality tv, and i notice that everyone is asking the same question, including my brother, who only watched the show once... i think i'd anwser.
i think you all are waaaay overlooking this whole thing. the explination for the removal of the men's shirts is probobly the easiest.
it's so you can see a difference in their weight loss. i'm not pretending that i know all the anwsers here, that reason could be wrong, but i'm guessing it's not, since it's the most logical. and i'm guessing a lot of people who watch it have a very liberal outlook on things and say "well... why can't women take their shirts off too!?" well, i'm guessing it's because the ratings would flop, if the women did, in the sense that a lot of very conservative people may watch that show, seeing as it's one of the reality shows on today with more substance and a more emotional plot. The women are probobly asked to keep their shirts on out of respect for less liberalminded viewers, and i'm sure the women have no problem with it.
if somebody would like to debate this with me, i'm all ears.