"House of Cards" actress Robin Wright, who recently became engaged to the actor, told OK! Magazine that she joined Foster on the diet out of solidarity.
"My fiance did a movie recently, playing Lance Armstrong, and he was on an 800-calories-a-day diet. I said, 'In solidarity, I am going to go on the diet with you,' even though I really want to go to an In-N-Out Burger," she said.
Foster follows in the footsteps of other actors who have taken extreme means to get into character — including Matthew McConaughey, Jared Leto
and Anne Hathaway
. Unlike these stars, however, Foster has to both capture the look and the power of someone capable of winning the grueling Tour de France seven times.
The film, directed by Stephen Frears, is based on Irish sports journalist David Walsh's book, "Seven Deadly Sins: My Pursuit of Lance Armstrong
." It will reportedly cover Armstrong's battle with testicular cancer, his cycling comeback, Tour de France victories, and finally, his fall from grace after a massive doping scandal. Foster's film is one of several currently in development about the disgraced cyclist.