David Letterman Expresses Mock Horror at Anne Hathaway's 25-Pound Weight Loss (Video)

Anne Hathaway takes some playful ribbing from David Letterman on Monday night's Late Show.

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Letterman asks the Les Miserables star how much weight she lost for the part of Fantine, a struggling mother who is forced into prostitution in 1800s Paris.

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She finally admits that it was a 25-pound weight loss, to which Letterman exclaimed: "Twenty-five pounds! I mean ... really? How did you do that?"

"Oh, you don't want to know," she replies. "It would just make you worry."

When Letterman tells her that she didn't look like she had "25 pounds to lose," Hathaway clarifies, "It wasn't so Fantine would look hot," before giving a massive spoiler to viewers who aren't familiar with the story line. (We'll refrain from including it here.)

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"It was all to look like she'd gotten really, really ill," Hathaway adds.

Les Miserables, which also stars Hugh Jackman, Russell Crowe and Amanda Seyfried, hits theaters Dec. 25.

Also on Monday's Late Show, Texas A&M University quarterback Johnny Manziel, the 2012 Heisman Trophy winner, presents the “Top Ten Perks of Winning the Heisman Trophy.”

Watch a clip from Hathaway's interview (warning: spoiler alert) as well as a preview of the "Top Ten" list below.

Late Show airs at 11:35 weeknights on CBS.