He's famous for his bulging muscles and delivering lines like "you hit like a vegetarian".
So when Arnold Schwarzenegger tells people they should eat less meat you can imagine the reaction he got.
Twitter soon filled up with people calling him a hypocrite, because as a bodybuilder he's eaten a lot of beef over the years.
The former bodybuilder has suggested the best way to cut down is to have a couple of meat free days a week.
This tweet sums up a lot of the cynicism online.
Arnie was speaking at the climate change talks in Paris.
"Right now people, seven million people are dying every year. That is alarming and everyone in government has the responsibility to protect the people.
"They have to do something about it."
He thinks that eating less meat would be a good way to start.
"28% of the greenhouse gasses come from eating meat and from raising cattle, so we can do a much better job."
Newsbeat was told recently by a climate expert that cutting back on meat consumption would help the environment.
Ellie Highwood, professor of climate physics at the University of Reading, told Newsbeat "if everyone around the world ate as much as we do in Britain, it would be even worse".
He was challenged about his meat eating and if it was possible to be as big as he has been as a vegetarian.
"Luckily we know that you can get your protein source from many different ways, you can get it through vegetables if you are a vegetarian.
"I have seen many body builders that are vegetarian and they get strong and healthy."
The comments have been backed by environmental campaigners and vegans.