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The total number of overweight and obese people in the world rose from 857 million in 1980 to 2.1 billion in 2013, a new study has found. That corresponds to a 28-per-cent increase in adults and up to a 47-per-cent increase in children.REGIS DUVIGNAU/Reuters

The most comprehensive study on obesity ever conducted reveals that obesity rates have risen everywhere in the world for the last 30 years and that some of the most dramatic increases are being seen in children and adolescents.

The researchers used sophisticated statistical tools to assemble existing worldwide data, fill information gaps and produce a report that offers a reliable comparison of 188 countries applicable to the last 30 years.

The global report, published Thursday in the prestigious medical journal the Lancet, notes that the obesity crisis is quickly spreading to developing nations, which will translate into more chronic disease and a major burden on worldwide health-care systems.

The total number of overweight and obese people in the world rose from 857 million in 1980 to 2.1 billion in 2013, the study found. That corresponds to a 28-per-cent increase in adults and up to a 47-per-cent increase in children.

The paper is unique because it is believed to be the first document that offers comparison of overweight and obesity rates globally from 1980 to 2013. Unlike other studies that focus on subsets of the population or only look at data from a given point in time, the information in the study paints a clear picture of how quickly obesity rates have escalated around the world.

The report, titled Global Burden of Disease Study 2013, is a "call for action" for governments to get this problem under control, said Dr. Ali Mokdad, one of the study's authors and professor of global health at the Institute for Health Metrics and Evaluation at the University of Washington.

The study comes days after a new report from the Organization for Economic Co-operation and Development found the financial downturn contributed to worsening the obesity crisis in part by forcing people in harder-hit countries to choose cheaper, less healthy food. And last week, the United Nations Special Rapporteur on the right to food warned that obesity is an urgent public health threat even greater than smoking.

Unless significant, sustained action is taken on a wide number of measures, the obesity epidemic threatens to cancel out any gains made in reducing rates of smoking, according to a commentary published with the new study.

"The solution has to be mainly political …" wrote Kim McPherson, a professor at New College, University of Oxford. "Politicians can no longer hide behind ignorance or confusion."

Canada's response to the obesity crisis has been dismal so far, according to Dr. Mark Tremblay, director of Healthy Active Living and Obesity Research at the Children's Hospital of Eastern Ontario Research Institute.

"I think we can be doing better," he said. "Governments are quick to proclaim that they're working on these things, but then if you dig in, not a whole lot is going on beyond declarations."

Dr. Tremblay says it's necessary to tackle obesity the same way as smoking: investing in a wide variety of public education campaigns, legislation, restrictions on promotion of unhealthy foods to children, along with other measures.

Health Minister Rona Ambrose said in a statement the government is taking concrete steps to tackle obesity, such as an eat-well campaign and $200-million in obesity-related research. "The rates of obesity in Canada are startling numbers, but they relate to a trend that is reversible," the statement said.

The report found that in 2013, 13 per cent of the world's obese people live in the U.S. and 15 per cent live in India and China.

Although the report found rates of obesity are higher in developed countries, they are gaining ground in developing countries. This particularly worrisome because it means the factors contributing to the problem here – prevalence of unhealthy food, the marketing of high-fat and high-sugar foods to children, lack of physical activity – are creeping into areas previously unaffected. Most developing nations don't have the money or infrastructure to take care of millions of people with heart disease, Type 2 diabetes or other problems related to obesity.

Over all, rates of obesity rose most between 1992 and 2002 in people aged 20 to 40. In recent years, the rate of weight gain in developed countries appears to be slowing down, which could be a signal that the obesity epidemic has reached its peak. Worldwide, 37 per cent of adult males and 38 per cent of adult females are overweight or obese. Among boys, 17 per cent were overweight or obese in 1980 compared with 24 per cent today. In 1980, 16 per cent of girls were overweight or obese, compared with nearly 23 per cent today.

In developed countries, men are more likely to be overweight or obese than women. In developing countries, the opposite is true.

In Canada, overweight and obesity rates are lower than the U.S., which has some of the highest rates in the world, but not by much. Nearly 65 per cent of Canadian men are overweight and obese; nearly 49 per cent of women are overweight or obese; nearly 26 per cent of boys under age 20 are overweight or obese; 22 per cent of girls under age 20 are overweight or obese.