Sep 23rd 2010 .
ONE IN six adults in the 33 mostly rich countries of the OECD is obese (measured as a body mass index of 30 or more) according to a report published on September 23rd. The fattest countries are Mexico and the United States, where around a third of adults are obese. Britain's adults are the biggest in Europe. By contrast, Asian OECD countries Japan and South Korea are the leanest. Governments will count the eventual cost: health-care spending on an obese person is 25% more than for someone of average weight. And the problem is not confined to the rich world. In rapidly developing countries such as China, Brazil and India obesity rates, though still low, are growing fast as the dietary habits of the ever-increasing middle classes change.