Obesity is, of course, not just bad for our individual health, it’s also bad for our economy. In the United States alone, an estimated $147 billion is spent each year on direct medical care costs associated with obesity. Billions more are also spent in indirect costs, such as lost productivity due to obesity-related health problems.
But, according to a provocative study published this week in the journal BMC Public Health, obesity has another, more hidden cost: Because of the energy (calories) needed to sustain our widening girths, obesity is putting a huge strain on the world’s food resources.
“When people think about environmental sustainability, they immediately focus on population. Actually, when it comes down to it, it’s not how many mouths there are to feed, it’s how much flesh there is on the planet,” one of the paper’s authors, Ian Roberts of the London School of Hygiene and Tropical Medicine, told BBC reporter Matt McGrath.
The heavier we are, the more calories we need to burn for energy — and, therefore, the more food we eat.
Using World Health Organization data from 2005, Roberts and his colleagues calculated the global adult human biomass for the world. It came out to be about 287 million metric tons. (A metric ton is equal to about 2,200 pounds.)
Of that total biomass, the researchers attributed 15 million metric tons to the excess pounds carried around by people who are overweight and 3.5 million metric tons to the extra weight on people who are obese. (In this study overweight was defined as a body mass index, or BMI, of more than 25; obesity was defined as a BMI of more than 30.)
Those extra metric tons of flesh, the researchers calculated, are the equivalent of 242 million people of average weight, or about 5 percent of the world population in 2005. (The average global body weight in 2005 was 137 pounds.)
U.S. is tipping the scale
The United States is responsible for a disproportionate share of that excess biomass. North America is home to 6 percent of the world’s population, the paper points out, but is responsible for 34 percent of its excess biomass. (Yes, North America includes Canada, but those percentages mostly reflect what’s happening in the U.S.)
“If every country in the world had the same level of fatness that we see in the USA, in weight terms that would be like an extra billion people of world average body mass,” Roberts told the BBC.
Asia, on the other hand, has 61 percent of the world’s population but is responsible for only 13 percent of its excess biomass. The average body weigh in Asia is 127 pounds compared to 178 pounds in North America.
U.S. versus Japan
Poverty may explain some, but not all, of the differences between these regions of the world, the paper’s authors say. “You can be lean without being really poor, and Japan seems to have pulled that off,” Roberts told the BBC.
If all the people in the world had Japan’s average BMI (22.9 in 2005), then the world’s total biomass would fall by 5 percent (14.6 million metric tons) — the equivalent of 235 fewer people of average weight in the world, the report states. This would decrease the world’s energy needs by an average of 59 kilocalories per day per adult — an amount that could feed about 107 million average-weight (by global averages) adults.
On the other hand, if all the people in the world had the U.S.’s average BMI (28.7 in 2005), then the world’s total biomass would increase by 20 percent (50 million metric tons) — or the equivalent of 935 additional people of average weight in the world. This would increase the world’s energy needs by an average of 261 kilocalories per day per adult — the amount needed to feed about 473 million average-weight (again, by global averages) adults.
“Our scenarios suggest that global trends of increasing body mass will have important resource implications and that unchecked, increasing BMI could have the same implications for world energy requirements as an extra 473 million people,” Roberts and his colleagues conclude. “Tackling population fatness may be critical to world food security and ecological sustainability.”