The Machine Gun Preacher star's new slimline figure has been criticised recently with some saying that he has gone too far.
But Butler is adamant there is no worry about his health as he's not as small as he may appear.
The 41-year-old told E! News: 'If I wear a long shirt, everyone says 'Oh my god, he lost so much weight!'
'But this is how I look. I just used to be a lot bigger. But now I'm surfing. I'm doing a surf movie so I have to slim down. I don't know...maybe I'm sick or something!'
He then joked: 'I ate my last meal in October and I run about 40 miles a day.'