New paper on food waste

Hall KD, Guo J, Dore M, Chow CC (2009) The Progressive Increase of Food Waste in America and Its Environmental Impact. PLoS ONE 4(11): e7940. doi:10.1371/journal.pone.0007940

This paper started out as a way to understand the obesity epidemic.  Kevin Hall and I developed a reduced model of how food intake is translated into body weight change [1].  We then decided to apply the model to the entire US population.  For the past thirty years there has been an ongoing study (NHANES) that has been taking a representative sample of the US population and taking anthropomorphic measurments like body weight and height. The UN Food and Agriculture Organization and the USDA have also kept track of how much food is available to the population. We thought it would be interesting to see if the food available accounted for the increase in body weight over the past thirty years.

What we  found was that the available food more than accounted for all of the weight gain.  In fact our calculations showed that the gap between predicted food intake and actual intake has diverged linearly over time.  This “energy gap” could be due to two things: 1) people were actually burning more energy than our model indicated because they were more physically active than expected (we assumed that physical activity stayed constant for the last thirty years), or 2) there has been a progressive increase of food waste.  Given that most people have argued that physical activity has gone down recently, which would make the energy gap even greater, we opted to for conclusion 2).   Our estimate is also on the conservative side because we didn’t accout for the fact that children eat less than adults on average.

I didn’t want to believe the result at first but the numbers were the numbers.  We have gone from wasting about 900 kcal per person per day in 1974 to 1400 kcal  in 2003.  It takes about 3 kcal to make 1 kcal of food so the energy in the wasted food amounts to about 4% of total US oil consumption.  The wasted food also uses about 25% of all fresh water use.  Ten percent of it could feed Canada.  The press has taken some interest in our result.  Our paper was covered by CBC news, Kevin and I were interviewed by Science and Kevin was interviewed on Voice of America.

[1] Chow CC, Hall KD (2008) The Dynamics of Human Body Weight Change. PLoS Comput Biol 4(3): e1000045. doi:10.1371/journal.pcbi.1000045