When a girl is not fat, and at this point in time she's usually do-able, if not hot, but you know deep down that at some point in her life, she's gonna be fat. It's just inevitable.
Dude 1: Hey man, you still dating that chick Lisa?
Dude 2: Yeah, I really like her, but I don't know about long term. I mean, she totally has fat potentiality.