Halve the amount of meat and sugar you eat to save the planet - experts
A "planetary health diet" requiring a massive shift from meat to vegetable consumption is needed to protect the well-being of future generations and the planet, according to experts.
Moving to healthier, more sustainable eating habits around the world could prevent 11 million premature deaths per year by 2050, scientists claim.
It would also reduce the damaging effects of climate change, soil erosion, deforestation and loss of biodiversity.
But the benefits come at a price. Red meat and sugar consumption would have to halve at least, while that of nuts, fruits, vegetables and legumes such as lentils and chickpeas must double.
By 2050, the world population is expected to reach 10 billion - but the Earth only has finite resources for food production.
Current diets, with a growing emphasis on Western-style high calorie foods laden with saturated fats, are pushing the planet beyond its natural boundaries while causing ill-health and early death, say the researchers.
The solution, based on three years of modelling studies, is a diet consisting of around 35% of calories obtained from whole grains and tubers, and protein mostly derived from plants.
While permitting variations based on local need and culture, the diet allows for an average of just seven grams of red meat per day and 500 grams of vegetables and fruits.
Daily poultry consumption would be confined to 29 grams - equivalent to one and a half nuggets - and fish to 28 grams, a quarter of a medium sized fillet.
Eggs would be restricted to around 1.5 per week.
The EAT-Lancet Commission brought together 37 experts from 16 countries specialising in health, nutrition, environmental sustainability, economics and politics.
Professor Tim Lang, one of the authors from City, University of London, said: "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.
"We need a significant overhaul, changing the global food system on a scale not seen before in ways appropriate to each country's circumstances.
"While this is unchartered policy territory and these problems are not easily fixed, this goal is within reach and there are opportunities to adapt international, local and business policies.
"The scientific targets we have devised for a healthy, sustainable diet are an important foundation which will underpin and drive this change."
Findings from the experts are reported in the latest issue of The Lancet medical journal.
Widespread adoption of the planetary health diet would improve intakes of healthy nutrients, such as non-saturated fats, minerals and vitamins, while reducing consumption of potentially harmful foods, they said.
Three computer models simulating the effects of the diet predicted that between 10.9 and 11.6 premature deaths could be averted per year. Adult death rates would be reduced by up to 23.6%.
The study authors recommended policies improving the availability of healthy food from sustainable sources, restricting advertising of unhealthy food, and promoting education campaigns.
Healthy food would also have to be affordable, and "social protection" for low-income groups may be needed to ensure they do not miss out, they said.
Effective governance of land and ocean use was also necessary to preserve natural ecosystems and maintain food supplies, said the report.
This would involved measures such as prohibiting land clearing, restoring degraded land, lifting fishing subsidies, and banning fishing from at least 10% of marine areas.
Levels of food waste would also have to be halved at least, said the experts. In high incomes countries, campaigns were needed to improve shopping habits and food storage, and help consumers understand "best before" and "use by" dates.
Professor Johan Rockstrom, from the Potsdam Institute for Climate Impact Research in Germany - who co-led the Commission, said a sustainable system that could deliver healthy diets for a growing and wealthier world population required "nothing less than a new global agricultural revolution".
He added: "Our definition of sustainable food production requires that we use no additional land, safeguard existing biodiversity, reduce consumptive water use and manage water responsibly, substantially reduce nitrogen and phosphorus pollution, produce zero carbon dioxide emissions, and cause no further increase in methane and nitrous oxide emissions.
"There is no silver bullet for combating harmful food production practices, but by defining and quantifying a safe operating space for food systems, diets can be identified that will nurture human health and support environmental sustainability."
US colleague and co-lead commissioner Dr Walter Willett, from Harvard University, said: "The world's diets must change dramatically. More than 800 million people have insufficient food, while many more consume an unhealthy diet that contributes to premature death and disease."
He added that the food group intake ranges recommended by the Commission were flexible enough to accommodate different agricultural systems, cultural traditions, and individual dietary preferences.
Complying with the diet would mean people in the UK slashing their meat consumption by 80%, according to the free-market think tank The Institute of Economic Affairs (IEA). This could not be achieved voluntarily, it maintained.
Christopher Snowdon, head of lifestyle economics at the IEA, accused the authors of the planetary health diet of campaigning for a "nanny state".
He added: "Their desire to limit people to eating one tenth of a sausage a day leaves us in no doubt that we are dealing with fanatics.
"They say they want to save the planet but it is not clear which planet are they on."