The United Nations marked World Food Day on Wednesday saying it was possible to eradicate hunger and stressing the importance of cutting food waste and ensuring balanced diets.

"We can win the fight against hunger," Jose Graziano da Silva, the director-general of the UN Food and Agriculture Organisation (FAO), said at a ceremony at FAO headquarters in Rome.

He said 62 out of the 128 countries monitored by the FAO had reached the Millenium Development Goal of cutting by half the number of hungry people from 1990 levels, showing the target was achievable by 2015.

The number of the world's hungry has gone down recently -- mainly thanks to economic growth in developing countries and higher farm productivity -- but still stands at 842 million people.

Graziano da Silva said the fallout from hunger cost about five percent of global income due to lost productivity and healthcare costs.

In a message for World Food Day, Pope Francis called for solidarity and an end to indifference to the plight of the hungry.

"It is a scandal that there is still hunger and malnutrition in the world," the pope said.

"Something has to change in ourselves, in our mindsets and in our societies," he said.

Ertharin Cousin, head of the World Food Programme, the UN food aid agency, told AFP in an interview that now was no time for "donor fatigue", and said some humanitarian crises around the world such as North Korea and Yemen risked being forgotten.

'The biggest challenge'

"The biggest challenge is ensuring we don't forget conflicts that are beyond the attention of the media," said Cousin, adding: "Food crises don't just affect the countries where people go hungry."

She also said the WFP was now giving vouchers to purchase food on local markets, following accusations that the agency has harmed small farmers by undercutting them with its aid supplies.

FAO official Dominique Burgeon said there was now also more in-country assistance for farmers to try and persuade people not to flee their homelands.

"It is an approach that developed especially after the crisis in Darfur in 2004-2005 and that we are now applying to Syria, Central African Republic and the Democratic Republic of Congo," he said.

"We noticed that sometimes people would have preferred to stay but were not receiving any aid" and were forced to move to camps, he said.

"If we do not support the people who want to rest, they become refugees or displaced," he added.

Another major theme being discussed on World Food Day is the cost of the 1.3 billion tonnes of food that go to waste every year -- around a third of the total food produced.

"With just a quarter of that, we could feed the 842 million hungry," said Robert van Otterdijk, an agriculture industry expert at the FAO.

Mathilde Iweins, coordinator of a report on the cost of food waste, said that "the agricultural areas used to produce the food that will never be eaten are as big as Canada and India combined".

But the FAO said focusing on the type of food being consumed was just as important, warning that bad diets place high costs on society.

About two billion people in the world lack vitamins and minerals that are essential for good health, while 1.4 billion people are overweight.

Children with stunted growth may be at greater risk of developing obesity and related diseases in adulthood, in a worrying cycle of malnutrition.

Of those overweight, "about one-third are obese and at risk of coronary heart disease, diabetes or other health problems", the FAO said.

The agency said that while wiping out malnutrition worldwide "is a daunting challenge, the return on investment would be high".

There are hopes that under-used, nutrient-rich staple crop species might come into fashion, as well as eating insects such as beetles.

The FAO said however that these initiatives must be backed up by global efforts to stem waste.

"Getting the most food from every drop of water, plot of land, speck of fertiliser and minute of labour saves resources for the future and makes systems more sustainable," the organisation said.