Obesity rates have stabilised in high-income countries in recent years, though levels remain unacceptably high, Ezzati added.
"Over 40 years we have gone from about 11 million to a more than tenfold increase to over 120 million obese children and adolescents throughout the world", lead author Majid Ezzati of Imperial's School of Public Health, told a news conference.
Among high-income countries, the United States had the highest obesity rates, where girls ranked 15th and boys ranked 12 worldwide.
Rates are highest in areas of Polynesia, the US and some countries in the Middle East & North Africa. By 2016, that number had risen to 124 million, with several million more children considered overweight but below the threshold for obesity.
Polynesia and Micronesia had the highest rates of child obesity previous year, at 25.4% in girls and 22.4% in boys, followed by "the high-income English-speaking region" that includes the United States, Canada, Australia, New Zealand, Ireland and Britain. Nearly two-thirds of these children live in South Asia, where some governments' ability to feed their citizens has been unable to keep up with countries' booming populations.
The percentage of boys and girls who are underweight correlates with poverty.
The study was published online Tuesday in the journal Lancet.
There are still more underweight than overweight kids in the world. While there are programs that target unhealthy foods, there are far fewer policies focused on making healthy food such as whole grains and fresh fruits and vegetables more affordable.
"The health consequences certainly are apparent in adulthood", she told CTV News. So we can't wait to deal with underweight, and then worry about overweight and obesity.
Dr. Nathalie Farpour-Lambert, the president-elect of the European Association for the Study of Obesity, said in a statement that obesity in childhood has a tendency to continue into adulthood, so that most who are obese as children will be obese into adulthood.
Over the next eight years, the United States is set to spend $4.2 trillion on treating obesity-related disease, Germany will spend $390 billion, Brazil $251 billion and the United Kingdom $237 billion if these countries do not do more to try to prevent it, the Guardian quoted the federation as saying.
"While it's happening also in the high-income world, especially in Europe and certainly in Japan and some of its neighbors like South Korea, it has been a slower process", Ezzati said.
Some experts said countries dealing with obesity should introduce or increase taxes on unhealthy foods and drinks, such as the taxes implemented in Mexico, Britain, South Africa and elsewhere.
It also offers advice on reducing the time children spend on sedentary activities and promoting more physical activity through recreation and sports.
"Comprehensive responses are needed to create healthy environments that can support individuals in making healthy choices grounded on knowledge and skills related to health and nutrition".