BRAZIL, June 20,2012 - People’s weight – not just population size – should be taken into account when planning how to deal with increasing pressure on the planet’s dwindling resources, say researchers from the London School of Hygiene & Tropical Medicine.

In a report to be widely launched at this week’s United Nations conference, Rio+20, researchers say that data from the UN and the World Health Organization show the adult human population weighs 316.4 tons, of which 16.5 tons is due to the overweight, and another nearly 4 million tones is due to obesity.

Rio+20 is a global conference being held in Brazil where leaders from 194 nations are working towards a series of new international agreements on sustainable development. The meeting marks the 20th anniversary of the UN Earth Summit in Rio, described by officials as a watershed meeting addressing topics as diverse as climate change and biodiversity.

The world population is over seven billion and the London researcher says that while all of these people need feeding, the energy requirement of a species depends not only on numbers but on its average mass.

The new research, which has been published in the open access journal, BMC Public Health, estimated the total mass of the human population, defined its distribution by region and determined the proportion of mass due to those who are overweight and obese.

Up to half of all food eaten is burned up in physical activity, the researchers note. Increasing mass means higher energy requirements, because it takes more energy to move a heavy body. Even at rest a bigger body burns more energy, they said.

While the average body mass globally was just less than 137 pounds, North America, which has the highest body mass of any continent, has an average body mass of 178 pounds. The continent has only 6% of the world’s population, but 34% of the world’s mass due to obesity. In contrast Asia has 61% of the world’s population but only 13% of the world’s biomass due to obesity.

If all countries had the same average BMI as the United States, the researchers say, the total human biomass would increase by 64 8million tons ‑ the equivalent of an additional 935 million people of world average body mass.

“Everyone accepts that population growth threatens global environmental sustainability. Our study shows that population fatness is also a major threat,” said Professor Ian Roberts, who led the London School research. “Unless we tackle both population and fatness our chances are slim.”

Sarah Walpole, another researcher on the London team, said the results “emphasize the importance of looking at mass rather than just population numbers when considering the ecological impact of a species, especially humans.”

This study was based on a World Health Organization report done in 2005, so researchers believe it actually represents an underestimate of the current situation. The world’s population is continuing to increase in size – the UN predicts that by 2050 there could be 8.9 billion people on the planet.




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