To keep climate change under 2 degrees Celcius, the average world citizen will need to eat 75 percent less beef, 90 percent less pork and half the number of eggs they are today, while tripling their consumption of beans and pulses and quadrupling the amount of nuts and seeds they eat, according to a new study published in Nature magazine.
We urgently need to dramatically reduce the global animal product consumption and food waste, as well as significant change to farming practices in order to ensure we can feed the estimated 10 billion people there'll be by 2050, the researchers found.
The University of Oxford's Marco Springmann, who led the research team, talks to Kathryn about their findings.
So what exactly is a flexitarian?
Someone who eats red meat once a week maximum and otherwise eats predominantly a plant-based diet of fruit, vegetables, legumes, nuts and whole grains, Dr Springmann says.
Dietary guidelines are often out of touch with scientific knowledge but this is as cutting edge as it gets, he says.
"Think about it as technological innovation, but an innovation for diet."
In Western countries, beef consumption needs to fall by 90 percent and dairy by 50 percent, the study found.
Animal farming – beef, in particular – is very resource-intensive, Dr Springmann says.
"Most animals need quite a lot of feed, and all that feed needs to be produced with water and fertilisers. An average cow needs about 10kg of grain feed to grow by 1kg, 6kg for pigs, 3 to 4kg for chicken."
He invites us to compare that to zero feed required by an average plant.
What the planet is asking of us nothing less than a regulatory and incentive system across the whole food chain, Dr Springmann says.
Less animal food production would reduce deforestation and freshwater consumption, but increased water efficiency will still be required and support given to farmers in adopting more sustainable and non-polluting practices, he says.
About a third of food produced around the world today never reaches a table – for different reasons in different countries, he says.
Reduction of food waste in low-income countries will require better food storage, infrastructure and transport systems, while reduction of food waste in high-income countries will require smaller packaging and better labelling, he says.
"There's really work to be done all along this chain."