The actress will start shooting her latest directorial project, which chronicles Olympian Louis Zamperini's survival after his capture by the Japanese during World War Two, later this month in Australia, and Gleeson has revealed he has lost "a lot" of weight for his role as war hero Russel Allen Phillips.
He tells Wenn, "I'm losing weight getting ready to shoot Unbroken with Angelina Jolie. I've gotten almost where I need to be; I've lost a lot.
"I kind of feel if I hadn't lost the weight we would have found a way around it, so this is a choice I made to be more authentic. It takes place on a raft and I start in two and a half weeks in Australia. I'm really looking forward to it."
The new film is based on author Laura Hillenbrand's biography about Zamperini, an athlete who competed at the 1936 Berlin Olympics.
He became a prisoner of war in 1943 when his U.S. Air Force plane crashed down in the Pacific and he was captured by Japanese soldiers behind enemy lines after spending over a month at sea without food or water.
Newcomer Jack O'Connell will play Zamperini in the movie.