Actor Zac Efron has said he wants to play an ageing rock star so he can gain more than 14kgs in weight.

The Hollywood heart-throb said building his physique for the upcoming Baywatch film had taken “a lot of hard work” and he was unsure if he would maintain it.

Speaking at the Los Angeles premiere of his new film Mike And Dave Need Wedding Dates, Efron said: “I would love to gain 14 kilos and play an ageing rock star. That would be an awesome transformation.

“I want to be honest with my characters. Otherwise, I’m just going to stay healthy fit.”

Efron, 28, has been sporting blond highlights in his hair for his role in Baywatch, the big-screen adaptation of the classic 1990s television series.

His latest comedy is based on the true story of brothers Mike and Dave Stangle, whose bid to find dates for their cousin’s wedding by placing an online advert on Craigslist went viral in 2013.

I want to be honest with my characters

It is the latest in a string of comedic roles for Efron, who found fame in Disney’s High School Musical films.

Efron’s co-star Alice Wetturlund said: “Honestly I’m amazed at his ability to do comedy. He approachesit as an actor so he’s very technical. He embodies the character perfectly.

“It’s mind-blowing, he’s so funny. I’m really excited at what he’s going to do.”

Anna Kendrick, Aubrey Plaza and Adam Devine also star in Mike And Dave Need Wedding Dates, which is released in the UK on August 10. (PA)