Natalie Portman never deprives herself and is a "pleasure-seeker".
The 29-year-old actress - who is currently pregnant with her first child - is little like her dark character Nina in psychological thriller 'Black Swan' because she doesn't like to "punish" herself, but preparing for the role she did have to do so to understand what being a ballet dancer can be about.
She told BANG Showbiz: "I'm very demanding of myself but I'm not self-punishing. I never think I've done enough, I always feel like I can do more but I don't like being hungry or in pain or tired.
"So for this character I sort of went into that self-punishing mode and didn't sleep and didn't eat and worked out all day through injuries for three months. But I was living in that character. On my own I'm a pleasure-seeker."
Among the preparations she had to undertake was five hours of exercise daily, something which she is glad she did because it made her understand the "discipline" of the dance world.
She said: "I started training a year before the film. I worked with a ballet teacher named Mary Helen Bowers who was a New York City ballet dancer for 10 years. We were doing five hours of training a day; three hours of ballet and then we would swim for a mile and tone for two hours.
"You really understand the discipline, the rigour and the willingness to work through physical pain. And also spending five hours a day with a former New York City ballet dancer for a year gave me a lot of stories".