The Food and Agriculture Organization (FAO) marks World Food Day on Wednesday, themed "Healthy diets for a #ZeroHunger world".
FAO said in a report on Monday that around 14 percent of the world's food is lost annually before reaching the retail level.
Reducing the figure would increase global economic growth and productivity, help fight world hunger and curtail greenhouse gas emissions, FAO said.
In the report, Qu Dongyu, FAO's director general, said: "I frequently wonder how we can allow food to be thrown away when more than 820 million people in the world continue to go hungry daily."
FAO makes a distinction between food "loss", measuring what is lost after harvesting or during transportation, and food "waste", referring to what goes off in supermarkets or is thrown away by consumers. In 2011, FAO suggested that around a third of the world's food was lost or wasted annually, but its latest report says that this was a "very rough" estimate.
The Rome-based agency said it would release an estimate on food "waste", completing Monday's data on food "loss", at a later stage. It also warned that tackling the problem was very difficult.
"While the reduction of food loss and waste appears as a clear and desirable objective, the actual implementation is not simple and its complete elimination may not be realistic," the report said.
Arif Husain, chief economist at UN World Food Program (WFP), said: "We are still unable to feed all people around the world. Without focusing on the major reasons causing hunger, like conflicts and climate, there is no chance to end it."
For instance, plastic packaging help preserve food for longer periods, however, it has been criticized due to the pollution caused by plastic wastes.
"Sometimes it can make sense (on an ecological level) to use plastic but it always depends on the situation," FAO expert, Andrea Cattaneo told the German News Agency.
On the occasion of the World Food Day, Qu Dongyu said: "One in every nine people in the world are hungry, even as the world produces a surplus of food. Two in five adults are overweight, and obesity is on the rise in almost every country in the world. For many people, better food supply and nutrition is a question of livelihood and income, as well as the affordability of nutritious diets."
The projected growth in both food supply and demand is uneven in all countries and regions, with the largest demand in Africa and South Asia, which are expected to be the most affected by climate change.
The report entitled "State of Food Security and Nutrition in the World 2019" reveals that the number of hungry people around the world has risen for the third year in a row. Hunger has particularly affected Africa, where one in five people are hungry. In Asia, the number of hungry people reached 515 million, in Africa 256.5 million, and in Latin America and the Caribbean 39 million. Stunting or short stature for age affects 149 million people, and nearly two billion people have moderate levels of food insecurity.
According to the report, the pace of progress to drop the number of stunted children and reduce the number of babies born with low birth weight is very slow. Thus, the nutrition goals emphasized in millennium development goal 2 (MDG 2) are out of reach. At the same time, in addition to these challenges, overweight and obesity persist in all regions, especially among school-age children and adults, according to the joint statement, pointing out that women are more likely to be food insecure than men on every continent, with the largest gap recorded in Latin America.
In this context, the heads of the UN agencies (FAO, WFP, IFAD, UNICEF and WHO), which issued the Food Security Report, said: "Our actions to address these disturbing trends are bolder, not just in scope but also in terms of multisectoral collaboration."