The group of international scientists said the greatest cause of greenhouse gas emissions is food production and the use of fossil fuels.
But while the use of coal and oil could be gradually replaced by renewable energy sources like wind and solar, the world will always need to eat.
As the world population increases it is feared that the production of food will become the main cause of climate change and environmental degradation.
The International Panel of Sustainable Resource Management pointed out that agricultural production accounts for 70 per cent of global freshwater production, 38 per cent of land use and 19 per cent of the world's greenhouse gas emissions.
The report, that will be presented to world governments, said the only way to feed the world while reducing climate change is to switch to more a more vegetarian diet.
"A substantial reduction of impacts would only be possible with a substantial worldwide diet change," it read.
Achim Steiner, Executive Director of the UN Environment Programme, said ordinary consumers can help fight climate change by eating less meat.
"The Panel have reviewed all the available science and conclude that two broad areas are currently having a disproportionately high impact on people and the planet's life support systems—these are energy in the form of fossil fuels and agriculture, especially the raising of livestock for meat and dairy products," he said.
Mr Steiner said governments could encourage people to eat less meat by reforming the system of taxes and subsidies so vegetarian food is cheaper.
"Smart market mechanisms, more intelligent fiscal policies and creative policy-making are among the options for internalising the costs of unsustainable patterns. Some tough choices are signalled in this report, but it may prove even more challenging for everyone if the current paths continue into the coming decades," he added.
Lord Stern of Brentford, the author of the influential Stern Review that first argued for economic measures to fight climate change, also believes the world needs to eat less meat.
He has already warned that the price of meat and other "carbon intensive" goods will need to go up to fight climate change.