Oy. Helps to read the report :p
The website is "Beautiful People". It seems to be like a mixture of HotOrNot and Facebook, where you need to meet a certain attractiveness level to be given access. What happened is people (noticeably) gained some weight and their attractiveness levels got too low.
If we want to be charitable (because the alternatives make my heart hurt): They were already "curvaceous" and this pushed them into the "slightly less attractive" category
If we want to burn people at the stake (possibly because we resent something or someone :p): A twig ate a sandwich
If we want to compromise: That website has very high requirements. Furthermore, these people are probably of the variety that actually monitor their weight very closely (as opposed to, "HOLY CRAP! I just lost 3 pounds by taking a dump. Awesome!"). And, as everyone knows, self-image and self-confidence are pretty important to appearance (how you carry yourself, what you wear). So if these people didn't feel "attractive" anymore, they probably looked somewhat frumpy. Thus making them seem even less "attractive".