Moving quickly when someone stops for you is just common decency, and fats have none of that, so of course they're not going to get out of your way.  When someone is kind enough to hold up traffic to keep me from getting squished, I do a quick walk (and with legs as long as mine that's actually faster than a full jog for most people). Since I'm in school, it's required by law to stop and let students cross in front of you.  Of course the fatties always take forever.  They're always late to class too, then make a ton of noise as they come in huffing and puffing.  Very annoying.  If you're late, you shouldn't get to come to class if you're going to disrupt lecture getting to your seat.