Scientists have unveiled what they say is an ideal diet for the health of the planet and its populations - including a doubling of consumption of nuts, fruits, vegetables and legumes, and a halving of meat and sugar intake.
If the world followed the "planetary health" diet, the researchers said, more than 11 million premature deaths could be prevented each year, while greenhouse gas emissions would be cut and more land, water and biodiversity would be preserved.
"The food we eat and how we produce it determines the health of people and the planet, and we are currently getting this seriously wrong," said Tim Lang, a professor at Britain's University of London, who co-led the research.
Feeding a growing population of 10 billion people by 2050 with a healthy, sustainable diet will be impossible without transforming eating habits, improving food production and reducing food waste, he said. "We need a significant overhaul, changing the global food system on a scale not seen before."
Many life-threatening chronic diseases are linked to poor diets, including obesity, diabetes, malnutrition and several types of cancer. The researchers said unhealthy diets currently cause more death and disease worldwide than unsafe sex, alcohol, drug and tobacco use combined.
The proposed planetary diet is the result of a three-year project commissioned by The Lancet health journal and involving 37 specialists from 16 countries.
It says global average consumption of foods such as red meat and sugar should be cut by 50 per cent, while consumption of nuts, fruits, vegetables and legumes should double.
For individual regions, this could mean even more dramatic changes. People in North America, for example, eat almost 6.5 times the recommended amount of red meat, while people in south Asia eat only half the amount suggested by the planetary diet.
Meeting the targets for starchy vegetables such as potatoes and cassava would need big changes in sub-Saharan Africa, where people on average eat 7.5 times the suggested amount.
Presenting the diet at a briefing on Wednesday, the researchers said they acknowledged it was very ambitious to hope to get everyone in the world to adopt it, not least because there is vast global inequality of access to food.
"More than 800 million people have insufficient food, while many more consume an unhealthy diet that contributes to premature death and disease," said Walter Willett of Harvard University in the US.
"If we can't quite make it, it's better to try and get as close as we can," he said.