High rates of childhood obesity are a problem in a rising number of low- and middle-income countries, according to a new global assessment of child malnutrition by UNICEF. It's the agency's most comprehensive nutrition report in two decades.
The report paints a complex, dire picture of the state of children's health. Overall, it found that around 200 million children under age 5, or 1 in 3 worldwide, are either undernourished or overweight. Wasting (below-average weight for height) and micronutrient deficiency remain persistent challenges in Africa and South Asia. Still, there's some good news: Stunting (below-average height for age) has dropped sharply in the last two decades on every continent except Africa.
Meanwhile, at least 340 million adolescents worldwide between ages 5-19, and 40 million children under age 5, have been classified as overweight, the report found. The most profound increase has been in the 5-19 age group, where the global rate of overweight increased from 10.3% in 2000 to 18.4% in 2018.
"It's a shockingly fast increase," says Laurence Chandy, director of UNICEF's Office of Global Insights and Policy and a lead author of the report. "It's hard to think of any development indicator where you see such a rapid deterioration."
Most of those children live in high- and middle-income countries in North America, Eastern Europe, Pacific island nations and the Middle East. The U.S. is near the top of the list, with a rate of adolescent overweight around 42% (the highest rates, up to 65% are in Palau, Nauru and other in Pacific island nations, which have long struggled with obesity driven by a heavy reliance on imported food).
But as processed food and beverages become cheaper and more widely available, levels of childhood obesity that were once the domain of rich countries are now occurring at lower and lower household income levels, particularly in Africa and South Asia. In 2000, only around one-fifth of low-income countries had an adolescent population in which at least 10% were classified as overweight; in 2016, three-quarters of those countries met that threshold.
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Low- and middle-income countries in which obesity was once rare are seeing some of the fastest increases: In 1990, Vietnam's adolescent overweight rate was one of the world's lowest, less than 1%; by 2016, it was nearly 10%. In South Africa, it jumped from 3.3% to 24.8%.
Yet the surge in developing-country obesity has not been met by a corresponding improvement in rates of undernourishment. Because processed foods are often high in sugar and low in essential nutrients, many poor families may face undernourishment and obesity simultaneously, the report found.
"A bad diet may often lead to obesity among adults and stunting due to nutritional deficiency among children," Chandy says. In some cases, the same child may be simultaneously stunted and obese. The report also warns of so-called "hidden hunger," in which a child may not be visibly malnourished but is deficient in essential vitamins and other nutrients, which can lead to impaired growth and immune system function.
Lindsay Jaacks, a global nutrition researcher at Harvard's T.H. Chan School of Public Health who was not involved with the UNICEF report, says the rise of childhood obesity in developing countries is an ominous sign for those countries' health-care systems. Those countries may soon face a costly burden of Type 2 diabetes, arthritis, cardiovascular conditions and other obesity-related conditions, she says. A separate study last week of obesity in rich nations by the Organisation for Economic Co-operation and Development, an intergovernmental group of the world's 36 highest-income nations, found that collectively, the group spends about $311 billion per year treating overweight-related conditions.
The change in poorer countries is happening faster than many researchers expected, Jaacks says, in large part because of the pervasive marketing of processed food, some of which may, intentionally or not, mislead parents.
"We're seeing there's a lot of confusion about what is healthy," she says.
In research interviews with parents in Malawi and India, Jaacks says, she found that many spent more money on processed foods than on fresh ingredients, often because snack products were labeled as containing nutrients — even if they were also loaded with sugar.
Some countries are taking legal steps to discourage children and their parents from buying unhealthy foods: Chile and Mexico both recently implemented a tax on sugary drinks, and this week Singapore announced plans to become the world's first country to ban ads for such beverages.
The most important opportunity to prevent childhood obesity is within the first thousand days after birth, says Sara Benjamin-Neelon, a child nutrition researcher at the Johns Hopkins Bloomberg School of Public Health. During that time, mothers should breastfeed as much as possible and especially avoid unhealthy food during an infant's transition to solid foods, a formative time for a child's metabolism.
Jaacks says researchers are also worried that poor households that currently don't have easy access to unhealthy foods may face increased risk as their countries' economic fortunes rise.
"In poor countries it's still the richer people who are more likely to be obese, but at a certain point in a country's development that reverses," she says. "So in five or ten years, the same people who are today suffering from undernutrition may be experiencing obesity. We want to get ahead of that curve."
In the meantime, the problem is likely to worsen — a separate study this month by the World Obesity Federation, a nonprofit coalition of nutrition research organizations, projected the number of obese children worldwide to grow by 100 million by 2030.
Fighting childhood overweight and undernutrition will require a combination of consumer education, government regulation of food labels and better food options in schools, Chandy says.
"What we have here is a problem that's the result of some success," he says. "Poverty levels have reduced enough that people have agency about what to buy, but then they have to make the right choices under various constraints, including markets which provide a limited choice of food with poor nutritional quality."