Long before he was dodging alien terraforming disasters on Mars or piloting a submarine through World War II, Matt Damon nearly wrecked his health for two days of screen time. The film was Edward Zwick‘s 1996 Gulf War drama ‘Courage Under Fire‘, and the role, a heroin-addicted army medic named Andrew Ilario, sent a 25-year-old Damon down a path so extreme it would change how he approached acting for the next three decades.
Damon lost around 50 pounds in just 100 days for the film, playing a medic dealing with heroin addiction and survivor’s guilt, even though he only had a handful of scenes. To pull it off, he lived on chicken, egg whites, steamed broccoli, and baked potatoes while running 12 miles a day. There was no nutritionist, no medical supervision, no safety net. Just a young actor determined to look the part.
Inside Matt Damon’s Crash Diet
In a Reddit AMA years later, Damon called it the most physically challenging thing he’d ever done, and admitted he basically “made it up” as he went, with no chef and no real plan beyond gut instinct. That improvising nearly cost him as the extreme diet brought the 5-foot-11 actor down to around 135 pounds. Director Edward Zwick reportedly got so worried by how emaciated Damon looked that he told him to start eating again, an order Damon ignored. After filming ended, Damon was diagnosed with deregulated blood sugar and needed medication, and it took roughly two years to get his body back to normal.
Damon has since talked about just how close he came to real danger. “I went too far. I got sick and I wouldn’t do that again because it was just too much,” he told The Independent. He recalled that the ordeal left him so weak he didn’t even have to act anymore. “I was a wreck,” he said. “I was getting dizzy spells and hot flashes.” He was warned, he’s said elsewhere, that the crash diet could have permanently shrunk his heart.
Why Matt Damon Says He’ll Never Do Extreme Weight Gain for a Role Again
That experience has quietly shaped nearly every physical transformation he’s done since, and it came up again recently in a much more public way. While promoting ‘The Odyssey‘ this month, Damon confirmed he’s done chasing extreme body changes in either direction. He said the dramatic weight gain he once did for roles like ‘The Informant!‘, where he packed on nearly 30 pounds to play whistleblower Mark Whitacre, is something he won’t do again. Damon actually called the opposite approach, losing weight the way he did for ‘Courage Under Fire‘, the truly dangerous one.
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Instead, Damon says he’s now focused on getting “really, really physically fit” through diet and lifestyle changes rather than big weight swings, and he’s stressed the need to be intentional about everything he puts into his body.
Matt Damon’s Weight Gain Warning to Josh Hartnett on the ‘Oppenheimer’ Set
The lesson has turned into something of a cautionary tale he now passes on to younger actors, though they don’t always listen. On the set of ‘Oppenheimer‘, Damon reportedly told co-star Josh Hartnett not to gain weight for his role as physicist Ernest Lawrence, only to find out Hartnett had already packed on 30 pounds.
Damon’s rule, as Hartnett later told on The Tonight Show, was simple. Don’t gain weight after 40, because your body will fight to keep it forever. Hartnett’s response, “Thanks, Matt. Thanks for telling me this now,” became a small, funny footnote to a much darker lesson Damon learned the hard way, three decades and one very hungry medic ago.
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