Chris Hemsworth (left) and bulked up for Thor (right)
Splash News Online; Zade Rosenthal
04/18/2011 AT 02:50 PM EDT
It wasn't weightlifting that wore out Chris Hemsworth as he bulked up – big time – to star in Thor
The actor, 27, says non-stop food consumption was the key to his 20 lbs. weight gain.
"I feel as if I've been busy, but all I've been doing is eating all day," Hemsworth tells Men's Health
in its May issue. "Eating when you're not hungry and taking in that amount of food is exhausting."
He continues: "I ask myself, 'Why am I eating this chicken? For protein. Why am I eating this broccoli? For vitamins and fiber. Why am I eating this Ho Ho?' "
And overeating wasn't the only lifestyle change for the Aussie actor as he prepared for the action flick, which is due in theaters May 6.
"It wasn't until Thor
that I started lifting weights," he says. "It was all pretty new to me."