Zac Efron says veganism changed his life

'The Greatest Showman' star shared his secrets with TeenVogue.com, saying: "Just like everyone else, I wake up, look in the mirror, and I see the imperfections and the bags under my eyes, and think, 'Oh, man, is this really the best I've ever looked? I'm getting older? What the heck?' "

He continued: "Recently what I've started doing is searching for the cure inside that's causing the symptoms of what I'm getting on the outside. Getting more sleep has really taken away the bags under my eyes, so I don't need to worry about it as much. There are other lifestyle changes - I've been experimenting with eating purely vegan. That's completely changed the way that my body works, and the way that I metabolize food, the way it turns into energy, the way that I sleep. It's been brilliant. It's been great for my exercise, and great for my routine."

Zac - who is currently filming the biopic for serial killer Ted Bundy - admits his on-screen beauty routine is "intense" but he prefers to be more relaxed with his grooming ritual on his days off and has stopped "caring" as much.

He explained: "Sometimes I love to let it all go out the window, and take a break from grooming for the entire week. And I love to be the guy that, three hours into my day, somebody close to me will be like, 'Dude, what's on your mustache?' And I'll be like, What the heck?' And it'll be the smoothie that I drank an hour ago, before all of my meetings that nobody chose to tell me about! I kind of just relax with it all. I don't really care as much anymore."

And Zac's tip for feeling good on the red carpet is to take "deep breaths" and wear a good suit.

He said: "A well-tailored suit always feels great before you go out, and a lot of deep breaths before the red carpet. Getting your picture taken - standing in this place and then told where to turn - is the most awkward you've ever felt, so you have to mentally prepare for that. Luckily, when I get to do it, I'm doing it in a cool suit, so I feel happy."