Baywatch actor Zac Efron has opened up about his reported "jaw-gate" in an interview with 'Men's Health' magazine.

The rumours surfaced last April, with many pointing out that he looked different in an Earth Day public service announcement.

Acknowledging that his appearance has changed in recent years, Efron explained that it happened after he fell at his home and broke his jaw in November 2013. His face and jaw muscles, as a result, have to work extra hard for him to make expressions, reports 'People' magazine.

A person's masseter muscle, which helps you close your mouth when you chew, along with the muscles on the face should operate "like a symphony", but his injury meant this was no longer the case, Efron said.

According to 'People', he was seeing a physical therapist to help him recover, but he briefly stopped while in Australia, where he shot Season 2 of his Netflix series 'Down to Earth' last year.

"The masseters just grew. They just got really, really big," Efron recalled.

'People' reports that it was his mom who told him about the attention his appearance was receiving online and about the speculation that he had plastic surgery or undergone some cosmetic procedures -- which the publication dubbed as "jaw-gate".

Efron noted that he typically tries to stay off social media, adding: "If I valued what other people thought of me to the extent that they may think I do, I definitely wouldn't be able to do this work."