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ScienceShot: The Weight of the World

The battle for our bulging waistlines is no longer just a health concern. A new report says we also need to consider the ecological effects of fat. Larger people require more food and energy, and with the United Nations projecting that there will be 9 billion humans by 2050, bigger bodies will gobble up even more resources. Researchers calculated the weight, or biomass, of the planet's adult population from data collected in 2005 by the United Nations, the World Health Organization, and the U.S. Agency for International Development. Measures included population size; a person's fat content, also known as body mass index; and height. Scientists found that the world's adult human population weighs 287 million tonnes. About 15 million tonnes was due to overweight people, and about one-third of that was due to the obese in North America, despite the fact that it contains only about 6% of the global population. Asia, meanwhile, accounts for 61% of the global population but only 13% of the world's overweight biomass is due to obesity in this region, the team reports online today in BMC Public Health. If populations in other countries begin to take after the United States, where 36% of the population is obese, the amount of energy required to support all that extra weight would increase by 481%.

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*This article has been updated for greater clarity.