“When people think about environmental sustainability, they immediately focus on population,” one of the paper’s authors, Ian Roberts, told the BBC. “Actually, when it comes down to it, it’s not how many mouths there are to feed. It is how much flesh there is on the planet.”
To get a sense of scale, here is a chart showing how many kilocalories a day were required per person in 2005, from a selection of countries:
“The weight of nations: an estimation of adult human biomass,” by Sarah C. Walpole, David Prieto-Merino, Phil Edwards, John Cleland, Gretchen Stevens and Ian Roberts. BMC Public Health.If all countries were as fat as the United States, the resulting increase in global weight would increase energy requirements by 261 kilocalories a day per adult. That’s the same as adding the energy requirements of 473 million adults of average B.M.I. to the planet.
“Tackling population fatness may be critical to world food security and ecological sustainability,” the authors conclude.