Is this why Brad Pitt looks so gaunt?

Brad Pitt appeared noticeably slimmer when he attended the premiere of The Lost City of Z in Los Angeles. Photo/AP

Six months after his wife Angelina Jolie filed for divorce, Brad Pitt has stepped out on the red carpet cutting a gaunt figure.

The 53-year-old made the rare appearance at the Los Angeles premiere of The Lost City of Z overnight.

Pitt kept his look low-key, wearing a flatcap and a simple black jacket over a white shirt.

Brad Pitt in Los Angeles. Photo/Getty

While the A-lister usually shows off his buffed-up bod in tight shirts and tailored jackets at Hollywood events, he looked noticeably thinner, with his baggy, loose suit pants hanging off his frame.

After laying low since his split from Jolie, he emerged last week, with photos showing a skinnier Pitt.

A source told People the star had "lost a few pounds" after working out "almost daily".

"He's healthy and much happier," the source said.

Brad Pitt in Madrid for the premiere of Allied in 2016. Photo/Getty

"Things with his family have improved, all is being addressed privately, and it's serving everyone in the family well."