We tend to think of obesity as a rich-country problem, but for several years now evidence has been building that the public-health hazard is assailing low- and middle-income countries as well, even as these same countries struggle with high rates of malnutrition. In perhaps the most comprehensive snapshot yet of this phenomenon, a study published in The Lancet on Thursday found that one-third of the world's population is now overweight or obese, and 62 percent of these individuals live in developing countries.
The graph below shows how the prevalence of overweight and obese men and women has risen between 1980 and 2013 in the developing and developed world, and as a whole. The research team—led by the Washington-based Institute for Health Metrics and Evaluation and funded by the Bill & Melinda Gates Foundation—defined "overweight" adults as those with a body mass index (BMI) between 25 and 30, and "obese" adults as those with a BMI of 30 or more.
These across-the-board increases translate into the global overweight and obese population ballooning from 857 million in 1980 to 2.1 billion in 2013. Men tend to have higher obesity rates in developed countries, and women tend to have higher rates in developing countries.
Obesity isn't just spreading to the developing world; it's also concentrating in certain places. According to the Lancet study, more than half of the world's 671 million obese people live in just 10 countries: the United States, China, India, Russia, Brazil, Mexico, Egypt, Germany, Pakistan, and Indonesia. The U.S. accounts for 13 percent of the world's obese population, and China and India a combined 15 percent.
But countries like China and India have massive populations, and their rates of obesity remain low relative to, say, America's. The maps below show the prevalence of obesity for adult men and women around the world. The darker the blue, the lower the rate. Yellow indicates a rate of 20 to 30 percent, and tan a rate of 30 to 40 percent. Orange and red represent rates of 40 percent or above. In China, for instance, the obesity rate for adult men is just under 4 percent; in the U.S., it's nearly 32 percent.
Prevalence of Obesity for Men 20 Years or Older (2013)
Prevalence of Obesity for Women 20 Years or Older (2013)
These trends are even more pronounced among children and adolescents, especially those in developed countries. The study found that while the global prevalence of overweight and obese adults rose by 28 percent between 1980 and 2013, the prevalence for children rose by 47 percent.
The researchers don't wade into the debate over the precise health effects of obesity, though they do state that being overweight puts people at greater risk for ailments like diabetes, cancer, and cardiovascular disease. And they don't theorize about why obesity rates are increasing, especially in the developing world. But others have hypothesized about the root causes, and the culprits are many, ranging from urbanization, to television, to rising incomes, to labor-saving technologies, to U.S. agricultural policies and junk-food exports.
Still, these broad trends over the last three decades distract from a more nuanced point: Growth in overweight and obesity rates was actually greatest between 1992 and 2002, and has slowed down over the past decade, particularly in developed countries. Yet while some progress has been made in wealthy nations, none of the 188 countries in the Lancet study have recorded significant declines in obesity since 1980. There are "no national success stories," the authors note.
That's the challenge facing governments around the world. How do you develop a strategy to reverse obesity rates when no country has successfully implemented one yet?