The world produces about 4 billion metric tons of food a year but 1.2 to 2 billion tons is not eaten, the study by the London-based Institution of Mechanical Engineers said. It is instead thrown away. Experts say food is wasted in both rich and poor countries, but for different reasons. Elliot Woolley teaches sustainable manufacturing at Loughborough University in Britain. He spoke at the Global Conference on Sustainable Manufacturing, which was held earlier this month in Vietnam. Mr. Woolley said in poor countries, food is usually lost while it is still in the field or during storage and transportation. He said that is because food producers there are inefficient. These businesses are unable to operate effectively without wasting materials, time or energy. But he added that once food is sold in developing countries, people usually eat everything they buy. However, people in developed countries throw away as much as half of the food they purchase. In the US, big contributors to waste include supersized portions that customers simply can't manage, and"eat as much as you want"offers in restaurants. In the UK, over-conservative sell-by dates on labels and two-for-one offers of perishable items are key factors, encouraging consumers to buy too much food to start with and to throw away items that have reached their sell-by date, but which are still edible. And efficient farming methods, transport and storage mean that most of the wastage occurs through retail and customer behavior. The British researcher called this custom"adisgrace". Elliot Woolley has created a smartphone app that he says shows users what food they have bought and when the food is about to become unsafe to eat. It also gives information on how people can combine the foods they have to make a meal. The software program is called"Pantry App". Mr. Woolley said that people who used the app reduced the amount of food they wasted by a third. But this result came from a limited experiment -- users only followed their food use for a week. Jeremy Bonvoisin is a student at the Technical University of Berlin. He attended the recent conference in Vietnam. He said one way to solve the problem of wasting food is to take steps to persuade people to stop buying so much food in the first place. He said people buy more food than they need because it is becoming less costly. They waste so much food because they buy more than they need. He said the new app could help those who already want to change the way they use the food they buy. But he is also worried that it could get people to waste more food because they no longer have to pay attention to how much they have bought. According to Elliot Woolley, the best way to stop wasting food in poor countries is probably    .
making people realize the bad effects of wasting food increasing the production and quality of grain limiting the transporting and storing of food improving their agricultural techniques