Meat is bad both for the health of people who eat too much of it and for the planet, a report says.

Aussies are the world's number one consumers of meat, but scientists warn our love affair with beef is killing us, and the planet.

An international team of experts has put lower meat consumption at the heart of a "planetary health diet" to stave off catastrophic damage to the environment.

The findings from the EAT-Lancet Commission warn the world's population is expected to reach 10 billion by 2050 and current diets, with a growing emphasis on Western-style high-calorie foods laden with saturated fats, are unsustainable.

The intake of meat and sugar needs to fall by half by 2050.

The 37 experts from 16 countries concluded that consumption of nuts, fruits, vegetables and legumes such as lentils and chickpeas must double.

People should think of meat as a treat and have "a burger once a week or a steak once a month", the report warned.

That would be a challenge to Australians who top the global list of meat eaters, with an average consumption per person of nearly 100kg of meat a year - or around 250g a day.

Under the report's guidelines, a person should eat only 7g or 15 calories worth of beef or lamb a day, which means Australians would have to cut 97 per cent of meat from their diet.

A single quarter-pounder burger patty weighs just under 114 grams - and forget substituting chicken.

The diet recommends no more than 29g of daily poultry - around one and a half chicken nuggets - and 13g of eggs, or one and a half eggs, a week.

The report also said livestock farming was "catastrophic" for the environment, producing up to 18 per cent of global greenhouse gases and contributing to deforestation and water shortages.

"To have any chance of feeding 10 billion people in 2050 within planetary boundaries we must adopt a healthy diet, slash food waste, and invest in technologies that reduce environmental impacts," the study states.

"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."

Ultimately, the new guidelines could globally prevent up to 11.6 million premature deaths per year, according to its creators.

Currently, nearly a billion people are hungry and another two billion are eating too much of the wrong foods, causing epidemics of obesity, heart disease and diabetes.