More than 2 billion people, accounting for one third of the world's population, are now overweight or obese a study has revealed.

In 2015 12 percent of adults and 5 percent of children globally were categorized as obese, according to the research published Monday in the New England Journal of Medicine. This equals a total of 603.7 million adults and 107.7 million children.

Being overweight while avoiding categorization as obese does not mean immunity to health risks. Data showed that a high Body Mass Index (BMI) accounted for 4 million deaths in 2015 globally, with nearly 40 percent occurring in those who were not obese. These were from a range of conditions including heart or kidney disease, diabetes, and cancer.

Among the world's 20 most populous countries, Egypt had the highest level of adult obesity, with this figure falling at 35.3 percent. The U.S. had the highest level of childhood obesity, at 12.7 percent.

At the other end of the scale, Vietnam had the lowest percentage of obese adults, while Bangladesh had the lowest number of obese children.

Countries clustered around the Persian Gulf such as Saudi Arabia, and Egypt had relatively high percentages of overweight and obese people.

The research took into account countries' sociodemographic index (SDI), which demonstrated that countries with the highest increases in obesity are those with low or middling SDIs, struggling with a prevalence of other forms of malnutrition at the same time. "These countries generally have limited financial resources for nutrition programs and mostly rely on external donors whose programs often preferentially target undernutrition; consequently, food security frequently takes precedence over obesity in these countries," the report explained.

The prevalence of obesity among children and adults has doubled in 73 countries since 1980. In addition, the rate of increase in childhood obesity in many countries has been greater than the equivalent figure for adult obesity.

Being categorized as obese means having a BMI of 30 and over. A BMI of 25 and over is considered overweight.

"People who shrug off weight gain do so at their own risk – risk of cardiovascular disease, diabetes, cancer, and other life-threatening conditions," Dr. Christopher Murray, author of the study and director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, said in the research's press release.

In July 2015, McKinsey & Company wrote that obesity costs the global economy $2 trillion per year, worth 2.8 percent of global GDP. This placed it as the second most costly health threat after smoking.

Dr. Ashkan Afshin, the paper's lead author and an assistant professor of global health at IHME, said in the release that: "Excess body weight is one of the most challenging public health problems of our time, affecting nearly one in every three people."

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