Obviously, build must have a lot to do with it since I'm 5'8.5" -275# and I'm wearing a size 22/24 pants and 16/18 top. I started out at size 30/32 pants (tight) and 26/28 tops (stretchy).

I've also found that how you like to wear your clothes and the types of clothes you wear makes a difference in what size you 'are' too. A lot of large people I know seem to prefer baggier clothes, but I've never been one of them, even at my heaviest. I don't wear them skin tight, but I prefer my stuff fitted as opposed to loose.