Lords of Dogtown star Emile Hirsch lost 41 pounds (18.5 kilograms) while making wilderness film IN THE WILD with Sean Penn - because the director insisted on the actor staying fit.
In the film Hirsch plays real-life adventurer Chris MCCandless, a top student who gave everything away to charity and hiked across Alaska, and Penn wanted his actor to get a taste of his character's struggles on the journey.
Hirsch says, "I went from 156 pounds when I got the part to 115 pounds, my lowest weight. I lost 41 pounds.
"I was perhaps a little bit overweight when I got the part, so I had to get into shape, and I kind of made it a lot harder on myself, being heavier than Sean wanted me to be.
"But I had a willingness to punish myself by working out... I'd do a full day of kayaking and hiking and then I'd be jumping on the treadmill for an hour every day."
Hirsch admits the vigorous fitness regime has turned him into a bit of a health nut: "A lot of the physical aspects have stuck with me. I still run a lot and I never ran before the film."