Nearly one in seven people suffer from malnourishment, the United Nations' Food and Agriculture Organization said on Wednesday in a report released ahead of a summit on sustainable development to be held in Rio de Janeiro next month.

"We cannot call development sustainable while this situation persists, while nearly one out of every seven men, women and children are left behind, victims of undernourishment," said FAO Director-General José Graziano da Silva.

"The quest for food security can be the common thread that links the different challenges we face and helps build a sustainable future. At the Rio Summit we have the golden opportunity to explore the convergence between the agendas of food security and sustainability to ensure that happens," he added, referring to the difficulties in ensuring that the poor have sustained access to food.

Despite significant progress in development and food production, hundreds of millions of people are not getting adequate nutrition because they lack the means to produce or purchase the foods required for a healthy and productive life, the UN food agency said.

The agency called on governments to invest in sustainable farming and food making, to cut waste and stop excessive consumption and to establish and protect rights to resources especially for the poor. 

The report predicts that if current consumption patterns persist, the world will need to increase food output by 60 percent by 2050 from levels in 2005 and 2007 in order to feed a population that is expected to rise to 9 billion from about 7 billion now.

However, experts say that it is possible to feed the population with a smaller rise in food production by making production and consumption more sustainable.

The agency said that food consumption and production systems should "achieve more with less," and besides reducing their negative environmental impacts, including soil and water depletion as well as greenhouse gas emissions, governments should work on cutting down on food losses and waste.

The report estimates that a third of world food production for human consumption, equivalent to roughly 1.3 billion tons of food a year, is wasted. 

"To 'beat the projections' we need to make bold policy decisions that will affect income growth patterns, changes in dietary preferences, levels of food waste and how agricultural production is used for non-food purposes," the report said.

The agency said that as the population rises with increased incomes and rising food demand, pressure on the world's agriculture and food systems and resources it relies on will also grow, and unless current global food production and consumption is revised, the agency predicts that millions more will suffer from chronic hunger in 2050.

"Worse, unless purposeful action is taken, the increase in food production of 60 percent needed to meet effective demand will still leave behind over 300 million people who are expected to suffer from chronic hunger in 2050 because they will remain without the means to access food," the agency said.