well...beer and bad nutrition have always been the "in" thing on college campuses.
you also have to consider there's a belief among many young women that upper-body exercise leads to small breasts, and big butts are popular, so pair that with the younger generation's thirst for high-fructose anything and you've got a recipe for flab.
what gets me are the girls who are simultaneously skinny and flabby... they might have no belly flab and be at their target weight, but they have no muscular definition their upper arms look particularly...odd.