John Goodman has lost a lot of weight.

The 63-year-old actor debuted his significantly slimmer physique on the red carpet Thursday at the premiere of his new movie "Trumbo" during the BFI London Film Festival.

The "Roseanne" alum has spoken publicly on multiple occasions about his fluctuating weight. In 2010 after having lost nearly 100 pounds, the Golden Globe winner told Men's Health how he'd struggled to maintain a healthy weight for most of life.

"It started when I was a kid. I'd lock myself in the house and sneak food," he said. "It gave me great pleasure to eat —it's part of an alcoholism personality."

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Goodman has been sober since 2007, and in doing so, he's been able to focus a lot more of his energy on living healthfully. Even so, though, it isn't easy. "It's a life of rehab," he told Men's Health of his more active lifestyle. "But it's a labor of love."

He also spoke with David Letterman on the "Late Show" back in 2010 about his then-recent slim down, admitting his "all-time" highest weight was around 400 pounds.

"It's going to be an ongoing process for the rest of my life," he reiterated, reassuring Letterman he never planned to slim down to the point where he might "look like Paris Hilton or anything like that."

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The best part, though? Goodman said he feels "night and day" better when he's working out and eating well.

For much more on how Goodman shed an estimated 100 pounds, tune in to E! News Friday at 7 and 11 p.m.

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