China has the second-largest number of obese people in the world behind only the United States, according to a pioneering study published in a leading international medical journal. Globally, there are 2.1 billion people classified as overweight or obese. Of that number, 671 million people were classified as obese, according to the report in The Lancet . Overweight means that a person has a body mass index - which factors in weight in relation to height - of 25 to less than30. With a BMI of 30 or more, a person is classified as obese. Childhood obesity in China is another issue that really needs attention Dr Marie Ng More than half of the world's obese population live in 10 countries, led by the United States with 86.9 million. Study data showed said there were 62 million obese people living in China last year, or more than 9 per cent of the world's total. Conducted by the University of Washington's Institute for Health Metrics and Evaluation (IHME), the study, the first of its kind, analysed data from 188 countries over 33 years and found that nearly 30 per cent (2.1 billion) of the world's population were either overweight or obese last year, up from 857 million people in 1980. Over the same period of time, the overweight and obesity rates among adults had increased for both men (to 37 per cent from 29 per cent) and women (to 38 per cent from 30 per cent). Lead study author Dr Marie Ng, assistant professor of global health at IHME, who had previously worked at Hong Kong University, told the South China Morning Post that although the overall prevalence of people being overweight or obese in China was relatively low compared to other countries, the total figure was "alarming" in terms of the consequent financial burden on the health system. "Childhood obesity in China is another issue that really needs attention," Ng said. "The proportion of obese boys, in particular, is almost double the proportion of obese men [at 6.9 and 3.8 per cent respectively]." Among the 188 countries studied, China had the fourth-greatest increase in overweight/obesity prevalence among children during the study period. In 1980, 5.7 per cent of people under 20 years old in the country were overweight or obese; last year, the number was 18.8 per cent. For adults (20 years and above), China had the 10th biggest absolute change in overweight/obesity prevalence, rising from 11.3 per cent in 1980 to 27.9 per cent last year. "Obesity is an issue affecting people of all ages and incomes, everywhere," said Dr Christopher Murray, director of IHME. "In the last three decades, not one country has achieved success in reducing obesity rates, and we expect obesity to rise steadily as incomes rise in low- and middle-income countries in particular, unless urgent steps are taken to address this public health crisis." The highest overweight and obesity rates were seen in the Middle East and North Africa, where more than 58 per cent of men and 65 per cent of women aged 20 or older were found to be either overweight or obese. Among children and adolescents, the prevalence of overweight or obesity increased by nearly 50 per cent between 1980 and last year. Last year, more than 22 per cent of girls and nearly 24 per cent of boys in developed countries were found to be overweight or obese. In the developing world, the figures for both boys and girls were about 13 per cent. In developed countries, the peak of obesity rates is moving to younger ages. The rise in global obesity rates over the last three decades has been substantial and widespread, presenting a major public health epidemic in both the developed and the developing world. Health risks such as cardiovascular disease, cancer, diabetes, osteoarthritis, and chronic kidney disease increase when a person's BMI exceeds 23. In 2010, overweight and obesity were estimated to have caused 3.4 million deaths, most of which were from cardiovascular causes. There is, perhaps, a little ray of hope from the report. The study found that in developed countries, increases in obesity that began in the 1980s and accelerated from 1992 to 2002 have slowed since 2006.