Around 124 million children and adolescents were found to be obese in 2016.
The research was conducted by scientists from Imperial College London (ICL) in the United Kingdom, in collaboration with the World Health Organization (WHO).
Prof. Majid Ezzati, of the School of Public Health at ICL, is the lead author of the study, and the findings were published in The Lancet.
More than 1,000 researchers examined the body mass index (BMI) of almost 130 million people living in 200 countries. This is the largest number of people to have ever been included in an epidemiological study.
Of these participants, 31.5 million were between 5 and 19 years old, and 97.4 million were at least 20 years old.
The BMI data for these people were gathered by examining 2,416 population-based studies. Prof. Ezzati and team then examined trends in BMI between 1975 and 2016 in an effort to determine childhood and adulthood obesity rates.
BMI measurements, as well as what counts as underweight and obese, were considered and defined according to standard WHO guidelines.
Childhood obesity 10 times higher
Overall, the study found that globally, total childhood obesity rates rose by more than 10-fold in the past four decades.
More specifically, in 1975, there were 5 million girls who were obese, and in 2016, this number rose to 50 million. The report counted 6 million boys with obesity in 1975, but this number spiked to 74 million in 2016.
Last year, an additional 213 million children and teenagers were found to be overweight.
Geographically, the highest increase in childhood obesity was observed in East Asia and in high-income, English-speaking countries such as the United States, Australia, Canada, Ireland, New Zealand, and the U.K.
The U.S. had the highest child obesity figures among high-income countries, and the Middle East and North Africa also saw some of the highest increases in child obesity during the past four decades.
And surprisingly, although obesity rates are on the rise, an increasing number of children are still underweight. In 2016, 75 million young girls and 117 million boys were "moderately or severely underweight."
However, the researchers note that if these trends continue, by the end of 2022 there will be more obese children in the world than underweight ones.
It is worth noting that adult obesity rates also increased, from 100 million adults in 1975, to 671 million in 2016.
Avoid ultra-processed, high-energy foods
Prof. Ezzati comments on the significance of the findings, saying, "These worrying trends reflect the impact of food marketing and policies across the globe, with healthy nutritious foods too expensive for poor families and communities."
"The trend predicts a generation of children and adolescents growing up obese and also malnourished. We need ways to make healthy, nutritious food more available at home and school, especially in poor families and communities, and regulations and taxes to protect children from unhealthy foods."
Prof. Majid Ezzati
"While there have been some initiatives led by governments [...] most high-income countries have been reluctant to use taxes and industry regulations to change eating and drinking behaviors to tackle child obesity," he adds.
"Most importantly," Prof. Ezzati continues, "very few policies and programs attempt to make healthy foods such as whole grains and fresh fruits and vegetables affordable to poor families."
"Unaffordability of healthy food options to the poor can lead to social inequalities in obesity, and limit how much we can reduce its burden," he warns.
"[Our] data also show," Prof. Ezzati says, "that the transition from underweight to overweight and obesity can happen quickly in an unhealthy nutritional transition, with an increase in nutrient-poor, energy-dense foods."
Dr. Fiona Bull, manager of the prevention of noncommunicable diseases program at the WHO, echoes Dr. Ezzati's thoughts. "WHO [encourage] countries to implement efforts to address the environments that today are increasing our children's chance of obesity," she says.
She adds, "Countries should aim particularly to reduce consumption of cheap, ultra-processed, calorie-dense, nutrient-poor foods. They should also reduce the time children spend on screen-based and sedentary leisure activities by promoting greater participation in physical activity through active recreation and sports."