Fat Amy's gonna need a new nickname.

Rebel Wilson, who hilariously played Fat Amy in "Pitch Perfect" and "Pitch Perfect 2," recently continued her slim-down process with a trip to the Ranch at Live Oak in Malibu, California.

"OMG just finished 4 fantastic days at #TheRanch4.0...so challenging but very rewarding! Not to mention I lost 8 pounds from marathon hiking over the 4 days!" Rebel wrote on Instagram on April 25, alongside a photo of her increasingly trim figure in action on a trail.

"Thanks to the amazing staff and masseuses (free daily massages are part of the program)!! Feeling great!! @theranchmalibu @fswestlake #TheRanch4.0 #theranchatliveoak," the funny lady added.

Since losing eight pounds in four days is no laughing matter, E! News did a little digging about Rebel's luxury bootcamp-style retreat and discovered a long list of celebs have taken advantage of the program.

Turns out Busy Philipps, Selma Blair, Jesse Metcalfe, Angela Bassett and Lea Michele have all spent time there, while Minka Kelly and Mandy Moore hit The Ranch together as part of a hike-centric, girls' getaway weekend.

"Thank you @theranchmalibu for leaving us feeling so empowered and ready to take on the world!!" Mandy wrote at the end of the pals' visit.

Empowerment aside, the Ranch is no place for the feint of heart. For one thing, a stay requires a $15,000 deposit (yikes) and a commitment to banning alcohol, caffeine, soy, gluten, dairy and processed sugars (so basically, all the fun stuff).

With "detoxification and revitalization" as the main goal for visitors, the program also features cooking demos and meals based on organic, vegetarian foods.

As for the exercise component, both the week-long and the four-day, "R4.0" program Rebel attended involve what the Ranch's website describes as "eight hours per day of rigorous exercise including four hours of morning mountain hiking, afternoon exercise classes and stretching."

And it seems to work. Last summer, Lea Michele checked in with InStyle shortly after returning from The Ranch, telling the mag, "we went on 12-mile hikes every single day for four hours … I can't even walk but it was the most amazing thing ever so I'm full-on wellness right now."