Who is the young man with whom Rita is obsessed in the novel, Fat: A Love Story?

Rita believes she is in love with Robert Swann, who is "tall, beautiful, upper-class, aristocratic. And thin." Looking like he just stepped out of Esquire magazine, Robert is a health nut and car fanatic who "was going to be a stockbroker like his dad, and make millions to add onto the millions they already had." Despite Rita's obsession with Robert, he remains a distant character.