New York Post reporter Mary Huhn had five pounds to lose before her wedding, and created what she is calling the Black Swan diet. It basically consists of eating only 1,200 calories a day—all vegetarian dishes (Portman is famously a vegan)—and doing "two hours of exercise a day—with a mix of ballet classes, swimming (Portman did a mile a day), circuit training and whatever extra cardio I could manage." This included several ballet classes, which might do wonders if you're doing it all the time, but a few hours a week isn't going to do more to tone the arms and work that core than a Zumba.
The problem with this whole endeavor, as Hahn mentions, is that Portman worked out five to eight hours a day for a year to get ready to show off her skeleton to the world. That's because Natalie Portman's job isn't really to be an actress, it is to be preternaturally beautiful. The same thing goes for Gwyneth Paltrow, Angelina Jolie, Britney Spears, Ryan Reynolds, and Tom Cruise. They are famous people with nothing to do but diet, exercise, and tend to their bodies and they have unlimited resources and all sorts of assistance to do so. The rest of us have jobs, strange food cravings, lazy days, and incidental circumstances that keep us from the gym. There isn't something fundamentally wrong with us, we're just normal.
I'm glad Hahn lost her five pounds and she looks great, but just cutting down her caloric intake and exercising more would do that, no matter if she employed this Oscar-nominated gimmick or not. Still we really need to stop attempting to transform our bodies into celebrity look-alikes. Trying to get Natalie Portman's bony arms (or Ryan Reynolds grating abs) is a losing gambit and endlessly vying to emulate her/him is only going to drive you as insane as she goes in the movie.