If the whole world had the same proportion of overweight and obese people as America, its biomass would rise by 20%

THE global obesity problem is hardly news, but fresh data continue to illuminate just how big that problem has become. In a paper published by BMC Public Health, Sarah Walpole and her colleagues examine the global distribution of biomass. In 2005 the world's adults had a collective biomass of about 287m tonnes. Overweight adults (those with a body-mass index over 25) comprised 5% of the total; obese adults (BMI over 30) comprised 1.2%. They were not distributed evenly. One tonne of human biomass accounted for 17 adults in Asia but just 12 in North America, where three-quarters of adults were overweight or obese, and where the total biomass due to obesity is almost 1.2m tonnes (see below). If the populations of other countries adopted the pattern of weight distribution found in the United States, the world's biomass would rise by 20%—roughly equivalent to adding an extra 1 billion average-sized people. This would create all kinds of strains, not least on the world's food supply.