"We can no longer feed our population a healthy diet while balancing planetary resources," they said, adding that addressing food insecurity was "an immediate challenge". About 35 per cent of our calorie intake should be from whole grain. Credit:The Healthy Grain Our main source of protein will need to be plant-based. Red meat should account for zero to no more than 14 grams of red meat a day, in line with the United Nations' Sustainable Development Goals to end hunger and the Paris Agreement on climate change. Roughly 35 per cent of our calories should come from whole grains, while our intake of legumes, nuts, vegetables and fruit should double, the commission advised in its report. The diet follows similar principles of the Mediterranean and Okinawa diets, the researchers wrote.

Illustration: Matt Golding Credit: "The world’s diet must change dramatically," said Dr Walter Willett from Harvard University, who co-led the commission - a collaboration of 37 experts in health, nutrition, environmental sustainability, food systems, economics and politics from 16 countries including Australia. The benefits of increased food production in the past 50 years are now being offset by the global shifts towards unhealthy diets, high in calories, sugars and animal-based foods, the commission authors said. The world's meat production is on an unstoppable trajectory and was a major contributor to climate change, the accompanying comment piece said. The world’s population will be 9.8 billion by 2050 and increasingly wealthy with an appetite for animal-based foods.

The commission argued that feeding us all will be impossible without fundamentally transforming current eating habits, improving the way we produce food and reducing waste. "The human cost of our faulty food systems is that almost 1 billion people are hungry, and almost 2 billion people are eating too much of the wrong food," the commission wrote. The authors made a suite of recommendations to shift the way we produce food and eat so as to stay within the planet's "safe" boundaries and to avoid potential ecological catastrophe from climate change and the destruction of biodiversity, land and fresh water, as well as nitrogen and phosphorus flows. Australians have one of the largest dietary environmental footprints per capita in the world, with emissions more than 200 per cent higher than comparable regions, driven by meat consumption.

Australians eat 95 kilograms of meat a year on average, markedly more than the OECD average of 69 kilograms, and we create about 3.1 million tonnes of edible food waste a year. "Imagine coming home to dinner after a long [day] at work but your family announce there is nothing to eat for dinner … again. Well, nothing decent anyway," said independent expert Sonia Nuttman from the School of Health and Social Development at Deakin University. Red meat production is on an "unstoppable trajectory", The Lancet says. Credit:Robert Rough "You are hungry, your kids are hungry, food is expensive and climate change is making it more difficult for farmers to grow food. The news reports another drought year (20 years to date), the Murray-Darling has dried up and water desalination plants are struggling to keep up with demand." Roughly 2 million Australians report being food insecure, and the issue of food security in Australia is expected to escalate, Dr Nuttman said. "The significance of this issue can be compared to the climate emergency".

Co-author of the commission’s report Tim Lang, from the University of London, said the food we eat and how we produce it determines the health of people and the planet. "We are currently getting this seriously wrong," he said. Adopting the "planetary health diet" would improve nutrient and micronutrient intake, and could avert 10.9 million to 11.6 million premature deaths a year, according to the commission’s modelling. Australian sustainability experts argue that limiting the ballooning global population would also be crucial. Credit:Graham Tidy Professor Lang said humanity had never tried to change the food system this radically at such speed or scale.

It will require unprecedented global co-operation and commitment, he wrote. The commission floated several strategies to transform global food systems and accelerate a shift to sustainable food production, including halving food waste, switching from high volumes of crops to varied nutrient-rich crops, and enacting policies to encourage people to make healthier food choices. Australian environmental and food security experts commended the report. Several argued that reining in global population growth would be crucial, and the switch to a predominantly plant-based diet "highly ambitious". Professor Bill Laurance, from James Cook University, said food security was "probably going to be the number one global challenge this century". But any campaign to reduce meat consumption should focus on health, rather than environmental benefits, he said.