(Cover) - EN Showbiz - Mark Wahlberg might play a "steroid abusing gym rat" in his upcoming film but he is "definitely not" using enhancements, says a source.

The actor is currently shooting comedy action film Pain and Gain alongside Dwayne Johnson. The two stars play bodybuilders in Florida who get caught up in an extortion ring and a kidnapping scheme that goes horribly wrong.

Mark has been pictured looking noticeably beefier during filming; leading to speculation he's using enhancements to bulk up.

However, an insider claims this certainly isn't the case.

"Mark Wahlberg definitely is not using any kind of enhancements to pump up," a source told US Weekly.

"Even though the film is about steroid abusing gym rats, he took it as a personal challenge to get to the size he is at now and has been training non-stop."

The insider added that Mark has been using "state-of-the art equipment" in between filming, and uses Dwayne to "inspire him to work harder."

Mark's representative has also denied the star has used steroids to alter his physique for the role. (C) Cover Media