Cleaning your plate may not help feed starving children today, but the time-worn advice of mothers everywhere may help reduce food waste from the farm to the fork, help the environment and make it easier to feed the world's growing population.
Hard data is still being collected, but experts at the Reuters Food and Agriculture Summit in Chicago this week said an estimated 30 percent to 50 percent of the food produced in the world goes uneaten.
The average American throws away 33 pounds of food each month -- about $40 worth -- according to the Natural Resources Defense Council, which plans to publish a report on food waste in April.
In a year, that means each person throws away almost 400 pounds of food, the weight of an adult male gorilla.
The U.S. Department of Agriculture estimates that 23 percent of eggs and an even higher percentage of produce ends up in the trash.
"We forget we have all these fresh fruits and vegetables, and at the end of the week we have to throw them away," said Esther Gove, a mother of three young children in South Berwick, Maine. "Now, I don't buy as much fresh produce as I used to."
Not sustainable if not eaten
But the impact of food waste stretches far beyond the kitchen.
Agriculture is the world's largest user of water, a big consumer of energy and chemicals and major emitter of greenhouse gases during production, distribution and landfill decay.
Experts say reducing waste is a simple way to cut stress on the environment while easing pressure on farmers, who will be called on to feed an expected 9 billion people around the world in 2050, versus nearly 7 billion today.
"No matter how sustainable the farming is, if the food's not getting eaten, it's not sustainable and it's not a good use of our resources," Dana Gunders, a sustainable agriculture specialist at the NRDC, said at the Reuters Summit.
In richer nations, edible fruit and vegetables end up in landfills because they are not pretty enough to meet a retailer's standards, have gone bad in a home refrigerator or were not eaten at a restaurant.
In developing countries, much food spoils before it gets to market due to poor roads and lack of refrigeration.
High food prices are another factor, since some people can't afford the food that's produced, said Patrick Woodall, research director and senior policy advocate for Food and Water Watch.
"It's not a situation where you have to massively ramp up production," Woodall told the Reuters Summit. "Even in 2008, when there were hunger riots around the world, there was enough food to feed people, it was just too expensive."
DuPont is working with farmers in Kenya to extend the life of raw milk. Often farmers have to travel up to 20 kilometers to get their milk to market, and due to the country's high temperatures, much of the milk gets wasted, Jim Borel, an executive vice president with DuPont, said.
"This has broad application, but we're focused on Africa right now," Borel said.
Making pizza toppings stick
Europe is a leader in tackling food waste, but the United States is catching on as producers, facing tepid sales growth, look to control costs.
For example, a General Mills pizza plant found a way to use heat to make toppings stick to frozen pizzas better. The system is expected to prevent thousands of pounds of cheese and other pizza toppings from going to waste each year.
The U.S. Environmental Protection Agency said 33 million tons of food waste hit landfills and incinerators in 2010, the largest solid waste product in the system. EPA has launched a program to address the issue.
Experts from EPA and other groups have floated a variety of recommended fixes. They say clarifying "sell by" and "use by" dates could help consumers avoid throwing food in the garbage too soon. Some food could be "rescued" and used in soup kitchens, while certain leftovers could be used as animal feed.
Increasing composting could boost soil health and drought resistance, while also easing the burden on landfills and reducing decomposition of garbage into greenhouse gas methane.
Gove, the Maine mother, has found her own solutions. She buys frozen blueberries and raspberries instead of fresh ones that may spoil; purchases meat in bulk; and freezes what she doesn't immediately need. She also has introduced her kids to frozen banana treats, which means she's able to keep the fruit longer.
"Milk is one thing we don't waste, though," she said. "My kids go right through it."
Researchers say people of every age -- especially children -- contribute to the food waste problem.
Gove said she has cut waste by starting with smaller meal portions for her children, who get more only when they ask. Still, she says, there is a limit to how far she'll go.
"I definitely don't want to get rid of my kids," she said.