WASHINGTON — Meat and dairy account for nearly half of the annual food loss each year in the United States as measured by value, according to data published recently by the Economic Research Service of the U.S. Department Agriculture. While meat (together with poultry and fish) ranks first in value among food categories wasted, near the bottom (sixth) in poundage wasted, following dairy, vegetables, fruits, grains and sweeteners. Calories wasted each year in the United States have reached 15 figures.

Food waste and the complexities of, the magnitude of and the challenges associated with addressing the problem are explored in an article in the current issue of Amber Waves published by the Economic Research Service of the U.S.D.A.

“Food Loss — Questions About the Amount and Causes Still Remain” was published June 2. Authors include Jean C. Buzby, Hodan Farah Wells and Jaspreet Aulakh of the E.R.S. Ms. Buzby, who has been studying food consumption issues for many years, is chief of the Diet, Safety, and Health Economics branch in E.R.S.’s Food Economics Division.

Per capita, 290 lbs of food went uneaten in 2010 in the United States, equating to a value of $371. This waste equates to 789 calories per person per day.

“The estimate of 290 lbs per capita at the consumer level in the United States in 2010 suggests that consumer level food loss in the United States is higher than in other parts of the world,” the authors said. “In general, food waste tends to be higher in developed countries — a 2011 study conducted for F.A.O. found that per capita food waste by consumers in North America and Europe was 209-254 lbs per year compared to 13-24 lbs per year in Sub-Saharan Africa and South/Southeast Asia.”

The economists noted overall percentage of food that is wasted or goes uneaten has been estimated at one third by the F.A.O.

“In the United States, an estimated 31% of the food available for consumption at the retail and consumer levels went uneaten,” the E.R.S. said.

While lower than the global average, the U.S. figure does not include losses in several parts of the food chain.

“E.R.S. defines food loss as the amount of food available for human consumption — after removing bones, pits, peels, and other nonedible parts — that is not consumed for any reason,” the economists said. “It includes moisture loss and cooking shrinkage; loss from mold, pests, or inadequate climate control; and food waste. Food waste is a subcomponent of food loss, and examples include edible food discarded by retailers due to color or appearance and plate waste thrown away by consumers. While E.R.S. researchers have estimated the amount of food loss that occurs in U.S. grocery stores, restaurants, and homes, the waste portion of this loss has not been calculated because of data limitations.”

The potential for spoilage and waste exists virtually at each link of the food chain, including field losses, problems during drying, milling, transporting, or processing that expose food to damage by insects, rodents, birds, molds, and bacteria. At retail, equipment malfunction (such as faulty cold storage), over-ordering, and culling of blemished produce can result in food loss.

“Consumers also contribute to food loss when they cook more than they need and choose to throw out the extras,” the economists said.

Losses occur at different parts of the “farm-to-fork food chain” when comparing what occurs in developed versus less-developed countries, the economists said.

In less developed countries, food loss mostly occurs closer to the farm and retail segments with relatively little wasted by the consumer.

“These countries tend to have relatively inadequate storage (particularly cold storage), transportation networks, and access to markets making it challenging to keep food edible and wholesome until it is consumed,” they said. “Access to loss-reducing technologies, such as sophisticated packaging films that allow fresh produce to breathe, and adoption of food management practices, such as computerized inventory tracking, are less common in developing countries.”

By contrast, in developed countries like the United States, a relatively larger share of food loss occurs at the consumer end of the spectrum.

“Food accounts for a relatively smaller share of household incomes, and consumers typically demand a wide variety of high-quality, cosmetically appealing, and convenient foods,” the economists said. “As a result, blemished, misshapen, or wrong-sized foods are often discarded to meet minimum quality standards. Also, oversized portions and the distaste for certain foods among abundant food choices may help contribute to greater plate waste. Additionally, consumers are often confused over “use-by” and “best before” dates, leading to the discard of edible food.”

The waste rate of 31% in the United States equates to an astonishing 141 trillion calories of food available in the U.S. supply in 2010 but not consumed.

When measured by calories (versus value or pounds, the top three food groups in terms of shares of total calories uneaten are very different, with added fats and oils most wasted, added sugars and sweeteners second and grains third. The relative ranking reflects, in part, these foods’ caloric density per pound.

The researchers recognized both the value of reducing food loss and limitations on how much progress is possible because of issues such as spoilage of perishable items and the cost of recovery.

“Consumers’ tastes, preferences, and food habits also play a role, such as when people throw out milk leftover at the bottom of a bowl of cereal,” the economists said. “Economic factors, such as the costs to recover and redirect uneaten food to another use, may only provide limited incentives to reduce food loss. Food firms will adopt a loss-reducing practice if it is economically justifiable, that is, if the benefits outweigh the costs.”

Ways cited in the research in which waste may be reduced include the adoption of technological enhancements in food packaging, more efficient food inventory management in retail stores and restaurants, increased redistribution of food to food bank networks and consumer education campaigns to reduce food waste.

One government effort toward this end is the U.S. Food Waste Challenge, launched a year ago by the Environmental Protection Agency and the U.S.D.A.

The program, targeted at U.S. producer groups, processors, manufacturers, retailers, local municipalities, and other government agencies, seeks to reduce food loss and waste; recover wholesome food for human consumption;  and recycle discards to other uses, including animal feed, composting, and energy generation.

“The goal of the challenge is to lead a fundamental shift in how Americans think about and manage food and food waste. Participants in the challenge include major food companies, smaller private firms, universities and colleges, sports teams, entertainment resorts, and other businesses,” the researchers said.

The Challenge program has a goal of 400 partners by 2015 and 1,000 by 2020.

Accurate measurement of food loss also is a challenge, the researchers said. The E.R.S. is working to enhance its estimates of food loss and to revise how it generates its estimate of food loss for fresh fruit, vegetables, meat poultry and seafood.