Former California Governor Arnold Schwarzenegger says people should go meat-free one or two days a week to protect the climate.
Meat-eating was an environmental problem, with farming creating an estimated 28% of global greenhouse gases, the body-builder and movie star told BBC News.
Asking people to go totally vegetarian would be too demanding, he said.
It would better to suggest giving up meat once or twice a week, he added.
When asked how young men would achieve a body like The Terminator - the cyborg assassin in the film of the same name - without steak, he said many successful body-builders avoided meat.
"You can get your protein many different ways," he told BBC News.
"I have seen many body-builders and (weight) lifters that are vegetarians.
"My friend recommends stop eating meat. I think that's a good idea but people won't buy in.
"People will buy in to stop eating meat one or two days a week - you have to start slowly. It's a very big challenge but it doesn't mean it shouldn't be done."
Livestock emissions
Most public debate on climate change focuses on industry, but emissions associated with meat-eating are causing increasing concern.
Producing 1kg of meat protein is calculated to take between 3 and 10kg of vegetable protein.
Emissions from farming, forestry and fisheries have nearly doubled over the past 50 years and may increase by another 30% by 2050, according to the United Nations.
Most of the emissions from meat farming come from belching livestock and nitrogen fertilisers.
Mr Schwarzenegger tackled the steak issue after an address to a packed hall of students at Paris's leading political science institute, Sciences Po.
His audience in the French capital hung on the words of a man old enough to be their grandfather, and applauded his optimism that climate change could be tackled.
As governor of California, Mr Schwarzenegger took on the oil and gas giants to cut carbon emissions through renewables.
He said his successor, the Democrat Jerry Brown, had increased his level of ambition - and the next governor would want to trump that.
He said it was pointless trying to persuade people to give up things they wanted, like big cars or jets. What was needed was technology to allow people to live the lives they want to live - but in a way that does not pollute.
Low-carbon drive
When asked about the promises from all the leading Republican Presidential hopefuls to scrap President Obama's climate laws, he said if he were in Washington he would make climate change a non-party issue through strong leadership.
The message clearly appealed to his audience, although some did not appear totally convinced.
On his earlier visit to the UN climate conference in Paris, he urged national governments not to ignore the role in tackling emissions that could be played by sub-national governments at the level of states, regions and cities.
Last week, the C40 group of mega-city mayors met in Paris to share ideas on cutting emissions. They say the movement towards the low-carbon economy is much deeper and wider than it has been in the past.
Follow Roger on Twitter @rharrabin
UN climate conference 30 Nov - 11 Dec 2015 COP 21 - the 21st session of the Conference of the Parties - will see more than 190 nations gather in Paris to discuss a possible new global agreement on climate change, aimed at reducing greenhouse gas emissions to avoid the threat of dangerous warming due to human activities.
Explained: What is climate change?
In video: Why does the Paris conference matter?
Analysis: Latest from BBC environment correspondent Matt McGrath
In graphics: Climate change in six charts
More: BBC News special report (or follow the COP21 tag in the BBC News app)
