That's interesting. At his heaviest, my boyfriend was 233 lbs at 6"1. He is currently about 190 now and I haven't noticed much of a difference aside from the fact that his stomach's got smaller. His face got a bit smaller too, but his overall look didn't change that much. I think he's well attractive either way.
Everything is soo individual. For some people a 40 lbs weight loss is the difference between being ugly and movie star handsome; for others it isn't as clear-cut. I do, however, think that if you are at a lower weight, you do tend to gain self-confidence, and that is ultimately what makes you more attractive.