CHAPEL HILL - If there's one New Year's resolution we can all share, it's to stop wasting food. More than 40 percent of all food produced in the United States goes unconsumed, according to Timothy Jones, a University of Arizona researcher. This national wastefulness costs us more than $100 billion annually, a sum larger than the GDP of Belize.

It also harms our environment. Food is the largest component of America's waste stream, and landfills are the country's leading methane emitters, with more than a quarter of the greenhouse gas released in the U.S..

Wasted food pervades all areas of the food chain -- from farms to restaurants, supermarkets to homes. It is household waste, though, that makes excellent fodder for New Year's resolutions.

There's plenty of room for improvement: more than 15 percent of the food we bring into our homes isn't eaten, according to Stanford's William Rathje, who tallied waste for 30 years. The average family of four tosses almost $600 worth of edibles each year, the University of Arizona's Jones found.

"I'm not that wasteful," you're probably thinking. But if you're under 60, you probably are. Most Americans who didn't live through World War II have never had to conserve food. Jones, an anthropologist, recalls one study participant denying any food squandering -- while scraping a plate of spaghetti and meatballs into the garbage. Skeptics might look for food rotting in the back of their refrigerators and in the trash can.

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While there are many causes of waste, simply not valuing food is high on the list. The relative cheapness of food encourages waste. Americans now spend just 10 percent of their incomes on food, the lowest it's been in 20 years. The "clean your plate" ethos has all but disappeared, replaced by an "eat what you'd like" mentality.

With obesity lurking in every food discussion, eating smaller portions is one way to merge those two ideas. Until that happens, saving excess food as leftovers reduces both overeating and waste.

Our fading food knowledge also triggers much squandering. Not knowing how long a casserole or quiche lasts causes many people to throw away food that's perfectly edible. Most leftovers remain good for a week if refrigerated promptly and kept under 41 degrees, says Angela Fraser, an N.C. State University food safety expert.

Our fast-paced lifestyle is another source of waste. With both parents working, there's less time to cook. But most folks haven't adjusted their grocery shopping habits to match, buying plenty of produce and fresh ingredients because they see themselves as healthy eaters. After a long day of work, many of us grab takeout food, bypassing the fresh veggies and meats until it's too late. Prepared foods such as washed and cut spinach, while convenient, don't last as long as whole foods.

Limiting the excess isn't difficult. Here are a few steps to reduce waste:

• Make a shopping list and stick to it. While that sounds easy, grocery stores are set up to sway you into impulse buys -- those cute baby bananas, for example. Planning out meals helps here.

• Don't shop hungry, when everything looks that much better. And try to go later in the week, to be sure foods are still fresh when you're home to cook.

• Avoid bag salads or pre-cut produce, if possible. They go bad faster because they're already peeled and chopped.

• Save leftovers from home-cooked and restaurant meals. Cornell University's Brian Wansink found that more than half of all major restaurant leftovers aren't taken home.

• Then, eat the leftovers, whether from the restaurant or home cooked. Wansink also estimates that -- aside from pizza -- more than half of all leftovers taken home are thrown out.

• Don't confuse the sell-by date with the use-by date. The former tells stores how long to display items, allowing shoppers time to eat them after buying.

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Following these steps will save you money and reduce the amount of food sent to landfills. Some waste, however, is unavoidable. Composting, when possible, is a positive way to handle that excess.

While we're talking about maximizing food use, here's another resolution: why not reduce waste outside your home by contributing time or money to food recovery organizations such as the Inter-Faith Food Shuttle or the Society of St. Andrew? Both groups' ability to recover edible food from restaurants, supermarkets and farm settings is limited by transportation budgets and volunteer participation. The Society of St. Andrew organizes gleaning events at which volunteers harvest crops that would otherwise be plowed under. There, literally lending a hand makes a difference in how much food is put to use.

Whether at farms or in your fridge, squandering food is often preventable. Otherwise, 2007 is going to be a real waste.

(Jonathan Bloom is a journalist in Chapel Hill writing a book on wasted food in America. He also maintains www.wastedfood.com)