Brie Larson avoided the sun for four months before shooting 'Room'.
The 26-year-old actress portrays Ma, a woman who has been held captive for years, in the movie and did a lot of research into how her physical condition would be, having been isolated for so long.
She said: "I spoke to doctors and nutritionists about what would happen to the skin, hair, nails and teeth given that she doesn't have a toothbrush, hairbrush or soap.
"There's very poor nutrition and no vitamin D so I worked with a nutritionist to go on a sparse diet and worked out with a trainer every day.
"I also had to stay out of the sun for three or four months before we started shooting. It's very hard to avoid the sun in LA. So it was long sleeves and a sun hat every day."
Brie has won a Golden Globe and been nominated for the EE Rising Star Award at the upcoming BAFTAs thanks to her role in the film, and though she's tipped to win Best Actress at the forthcoming Academy Awards, she isn't getting too excited.
She told Stylist magazine: "I don't know [if the buzz is helpful], we'll see if people go and see the movie.
"It's like talking about a fantasy wedding when you don't have a boyfriend."