While, Angelina Jolie is now promoting "Unbroken" - her directorial movie based on the life of Louis Zamperini, a World War II prisoner of war survivor and Olympic distance runner - fans gain interest on her concerning weight loss.

The "Maleficent" star did not address any issue concerning her weight or health during in her appearances to promote the film, but when cast of the movie "Unbroken" were interviewed by HuffPost Live, the secret to the 39-year-old Hollywood superstar's skinny frame was revealed.

"She was so determined. I was also surprised how skinny she got. You know, she was not eating much. I felt so bad I was the only one who got fat during filming," Japanese actor and one of the "Unbroken" cast Miyavi revealed.

Most of the stars in the film also lost weight - Garrett Hedlund, Jack O'Connell and Finn Wittrock - all admitted that they had to go on a diet for their roles.

Angelina Jolie's controversial weight loss have gained the interest of entertainment publications for years now, in 2011 In Touch Weekly previously reported that Brad Pitt's wife shares a bizarre diet and a source allegedly close to the actress claimed that she had food "obsessions."

"Her daily diet varies. Sometimes it will be just green tea and nuts. Other days, it will be red meat and red wine, and then, back to tea and some tiny portion of protein."

Angelina Jolie previously discussed the difficulty of filming "Unbroken" (World War II biopic) when she spoke with Entertainment Weekly.

"On set, we started to joke and say, 'Tomorrow will be easier,' knowing full well that on this challenging shoot, there are no easy days," "Maleficent" star told the publication through email.

"Anytime it gets tough, we think of the real men who lived through this, and no one complains. In fact, we all just feel honored to be here."

"Unbroken" is Angelina Jolie's directorial movie about the story of American Olympic runner and World War II hero Louis Zamperini, who was imprisoned by the Japanese army.

The film, which is said to gain Oscar success, is scheduled to hit theaters on December 25 starring actors Jack O'Connell, Garrett Hedlund and Domhnall Gleeson and Miyavi.

Angelina Jolie further discussed her work with "Unbroken" during an appearance on "The Daily Show" which you can watch below: