Jan. 23 (UPI) -- Americans may be guilty of ignoring the old axiom "waste not, want not," a new analysis suggests.
In findings published Thursday in the American Journal of Agricultural Economics, researchers from the College of Agriculture Sciences at Penn State University note that U.S. households waste nearly one-third of the food they acquire.
The researchers estimate that consumers waste $240 billion worth of food annually, or an average of roughly $1,900 per household.
"According to the U.N. Food and Agriculture Organization, food waste is responsible for about 3.3 gigatons of greenhouse gas annually, which would be, if regarded as a country, the third-largest emitter of carbon after the U.S. and China," study co-author Edward Jaenicke, professor of agricultural economics at Penn State, said in a statement.
This food waste has implications for health, food security, food marketing and climate change, he added.
Jaenicke and his colleagues analyzed data from 4,000 households that participated in the U.S. Department of Agriculture's National Household Food Acquisition and Purchase Survey, known as FoodAPS, with food-acquisition data treated as the "input."
FoodAPS also collected biological measures of participants -- including height, weight, gender and age -- enabling the team to apply formulas from nutritional science to determine metabolic rates and calculate the energy required for household members to maintain body weight, which was considered the "output."
The difference between the amount of food acquired and the amount needed to maintain body weight in their analysis represented the measure of uneaten, and therefore wasted, food.
In addition, demographic data collected as part of the FoodAPS survey was used to analyze the differences in food waste among households with a variety of characteristics -- for example, households with higher income apparently generate more waste, and those with healthier diets that include more perishable fruits and vegetables also waste more food.
Overall, the team found that the average American household wastes 31.9 percent of the food it acquires. Additionally, they noted that more than two-thirds of households in the study wasted between 20 percent and 50 percent of the food they acquired.
Even in the least wasteful households, 8.7 percent of the food acquired goes uneaten.
Households associated with less food waste include those with greater food insecurity -- especially those that participate in the federal SNAP food assistance program, more commonly known as "food stamps" -- as well as those households with a larger number of members. Other households with lower levels of waste included those that use a shopping list when visiting the supermarket and those who must travel farther to reach a grocery store.
"This suggests that planning and food management are factors that influence the amount of wasted food," Jaenicke said. "People in larger households have more meal-management options. More people means leftover food is more likely to be eaten."
Avoiding waste is also challenging for consumers because some grocery items are sold in sizes that may influence waste, he added.
"A household of two may not eat an entire head of cauliflower, so some could be wasted, whereas a larger household is more likely to eat all of it, perhaps at a single meal," he explained.
The Penn State researchers noted that their findings were consistent with earlier studies, which have shown that 30 percent to 40 percent of the total food supply in the United States goes uneaten -- meaning that resources used to produce the uneaten food, including land, energy, water and labor, are wasted as well.
Beyond the economic and nutritional implications, reducing food waste could be a factor in minimizing the effects of climate change, they said, because discarded food is a major source of greenhouse gas emissions.
"While the precise measurement of food waste is important, it may be equally important to investigate further how household-specific factors influence how much food is wasted," said Jaenicke. "We hope our methodology provides a new lens through which to analyze individual household food waste."