Credit: D Dipasupil/FilmMagic

Bad Teacher star Jason Segel has undergone a serious slimdown.

Having once ballooned to a whopping 245 lbs., the 31-year-old Segel was inspired to put down the burgers and booze when he saw a set of unflattering pics his assistant took without his knowledge.

Binging on "the best food and booze anywhere" in New Orleans while filming a flick, Segel told David Letterman during a Thursday appearance on The Late Show that the photos served as an intervention of sorts.

"Unfortunately my assistant had a key to my room in case I overslept," the actor told the Late Show host. "She came in one day to wake me up and she took a bunch of pictures to show me what I had become."

Dropping 30 pounds, the slimmed-down Segel showed Letterman one of his fat photos, taken with Taco Bell wrappers strew about.

"Honest to God, Jason, this looks like a crime scene!" Letterman remarked.