Liam, 25, his "Hunger Games" co-star Woody Harrelson to persuade him to become vegan, reported E!online.
"I have a lot of friends who are vegan. Woody Harrelson was actually one of the original reasons I became vegan, because he's been vegan for, I don't know, 30 years or something.
"So, with the facts I was gathering, and then just how I was physically feeling, I felt like I had to do something different, so I adopted this vegan-diet lifestyle. It's been almost five months now," he said.
"Chris is extremely healthy and has played Thor and has had to work out a lot over the past few years. But he has a lot of digestive issues, and he's constantly trying to figure out what's best for his system. Through talking to me, he's somewhat adapting, I think, to eating more vegetables and more plant-based stuff," he said.