How Zac Efron Got His Eight Pack

The 28-year-old actor appears in the new film "Dirty Grandpa."

Zac Efron shows off his impressive eight pack in his new film Dirty Grandpa – but it’s been hard earned.

The 28-year-old actor avoids processed foods and sugar. He also works out an hour a day, completing crunches and bicep curls.

Read: Teen Movie Critic Apologizes After Amy Schumer Slams Him For Sexist Joke

All that gym time must be keeping him busy. The actor didn't appear at the 10th anniversary reunion special for High School Musical, in which he starred as a teen. His absence had some fans fuming.

“Is Zac Efron a snake for not turning up at the HSM reunion? You can bet on it, bet on it, bet on it,” one wrote.

Efron is tied up promoting his upcoming movie Dirty Grandpa, but will record a message to air during the special. The tribute will air on the Disney Channel on Wednesday at 8 p.m.

Watch: Woman Poses With Her Former Self After 150 Pound Weight Loss