Justin Bieber drove his fans wild on social media Thursday as he posted pictures of himself pumping iron.

The 20-year-old self-professed gym rat appears determined to grow out of his scrawny teenage image and has been working out regularly in a bid to buff up.

And Justin had his Instagram and Twitter followers nearly fainting Thursday afternoon, when he posted a collage of five snaps that showed him exercising while showing off his many tattoos.

“Back in the gym #dontbescared #orangegymrats,” he captioned the images.

Within minutes, the post had clocked hundreds of thousands of likes on Instagram.

“Come back to brazil,” one fan pleaded (sic).

“No cause he's mines,” another wrote (sic).

The post came days after rumours surfaced Justin’s on-again, off-again girlfriend Selena Gomez had become increasingly concerned about her own body in order to keep Justin interested.

Apparently the pressure has been mounting, with the former Disney star reportedly considering drastic measures in order to impress the pop star.

“Selena is putting a huge amount of pressure on herself to be sexy because she’s afraid of losing Justin,” an insider revealed told HollywoodLife.com. “She’s been asking people if they think she should get her boobs done because all the girls he was with have bigger boobs than her.”

Selena and Justin first began dating in 2010 but split at the end of 2012.

In between being seen together, Justin has been photographed with a number of beautiful women, reportedly causing Selena’s insecurities to bubble up.

“She feels like she needs to be the hottest girl in the world to keep his attention. She’s studied every girl that he hooked up with while they were broken up, at least the ones she knows about, and compared herself to them down to every last detail,” the source continued. “For God knows what reason, Selena has really low self-esteem, she has a long list of things she thinks she could improve as far as her appearance. Even though she’s so beautiful she sees all kinds of flaws when she looks in the mirror.”

Spokespersons for the stars have not commented on the claims.