This Is Us star Chrissy Metz’s gargantuan girth might fill out a room — but it’s her titanic ego that really takes up space on set!

Her backstage backbiting is destroying NBC’s hit show, claimed a snitch who spoke exclusively to Breaking Celebrity News.

“Chrissy’s been throwing her weight around like a bull in a china shop,” the source spilled.

“She snaps at makeup people, she won’t take direction, and she has fits because wardrobe has the toughest time fitting her!”

The actress, 36, signed up for the NBC series knowing she’d have to drop weight from her massive, 400-pound frame.

But now Breaking Celebrity News has learned the pressure to slim down and sudden stardom have amped up her diva demands.

The source said the stress is making Metz not only a giant pain in the butt but also someone who is gobbling up her co-workers’ goodwill and patience!

“She boasts she’s lost 100 pounds, but she’s already gained a lot of it back,” said the insider. “Now she’s complaining the stress of the show is making her even hungrier!”

Queen-sized Metz got her big break with the role of Ima Wiggles on American Horror Story: Freak Show.

But her breakout success playing weight-challenged Kate Pearson on This Is Us has sent her over the edge, according to sources.

“Chrissy panics whenever she has to do a red carpet,” the insider said. “She hates watching people whisper how fat she is.”

Though her rep denied any problems, the stressed-out diva is back to wolfing down 5,000 calories a day, .

“She’ll pound an entire pack of doughnuts at once!” tattled the source. “The production assistants have to go through her dressing room and toss out all the junk food she’s stashed away.”

Metz caused even more tension on the set by failing to tell bosses about her failed marriage to British journalist Martyn Eaden.

“She never mentioned it, so everyone was surprised to learn about it,” a show spy sneered.