VATICAN CITY (Reuters) - Pope Francis on Wednesday denounced what he called a "culture of waste" in an increasingly consumerist world, and said throwing away good food was like stealing from poor people.

"Our grandparents used to make a point of not throwing away leftover food. Consumerism has made us accustomed to wasting food daily, and we are unable to see its real value," Pope Francis said at his weekly audience in St Peter's Square.

"Throwing away food is like stealing from the table of those who are poor and hungry," he added.

Since taking office in March, Pope Francis has said he wants the 1.2 billion-strong Roman Catholic Church to defend the poor and to practise greater austerity itself. He has also made several calls for global financial reform.

Around 1.3 billion tonnes of food, or one-third of what is produced for human consumption, gets lost or wasted every year, according to the United Nations' food agency.

In the industrialised world, the majority of waste is by consumers, often because they buy too much and have to throw away what they do not manage to eat.

A United Nations-backed study released on Wednesday said simple measures such as better storage and reducing oversized portions would sharply reduce the vast amount of food going to waste.

In United States restaurants, diners wasted 9 per cent of the meals they bought, partly because of a trend of increasing the size of everything from cheeseburgers to soft drinks, said the report by the World Resources Institute and the UN Environment Programme.

Pope Francis said the "culture of waste" was especially deplorable given the prevalence of hunger in the world. The UN says hunger affects some 870 million people, while two billion suffer from at least one nutritional deficiency.

The Argentinian-born pontiff warned that too much focus on money and materialism meant financial market dips were viewed as tragedies, while human suffering had become normal and ignored.

"In this way people are discarded as if they were garbage," he said.