Americans are wasting food at a rate of 1,400 calories per person per day which has implications for obesity and climate change, U.S. researchers say.

Decomposing food waste emits the greenhouse gases methane and carbon dioxide, say the scientists, and producing and cooking food that doesn't get eaten burns excess fossil fuels, as well.

Kevin Hall and his colleagues at the U.S. National Institutes of Health found that food waste in the U.S. has increased by about 50 per cent since 1974. They estimate the current yearly food waste in the U.S. at 150 trillion calories.

The researchers came to their calculations from the difference in the energy content between the U.S. food supply and the amount of food eaten by the American population.

They estimated the amount of food eaten in the country by using a mathematical model of human metabolism that relates body weight to the amount of food eaten.

Hall and his colleagues relate the amount of food waste to the U.S. obesity epidemic and suggest that both are the result of an excess supply of cheap, readily available food.

"Addressing the oversupply of food energy in the US may help curb the obesity epidemic as well as decrease food waste, which has profound environmental consequences," they wrote in the journal Public Library of Science ONE.

Link to greenhouse gasses

The environmental impact of food waste stems from the greenhouse gases that result from its preparation and decomposition. Methane from food waste rotting in landfills is 25 times more powerful a greenhouse gas than carbon dioxide.

Also because agriculture uses about 70 per cent of the fresh water supply, the researchers estimate that food waste represents a significant waste of water, as well.

"Food waste now accounts for more than one quarter of the total freshwater consumption and 300 million barrels of oil per year," the researchers wrote. That represents about four per cent of the total U.S. oil consumption.

Although there is no similar data for Canada, World Vision Canada says that in Toronto alone, more than 17.5 million kilograms of food is thrown out every month.

In Britain, the government's Waste & Resources Action Programme estimates that $17.5 billion worth of food is wasted every year.