Obesity and smoking are the two main drivers behind the soaring numbers of cancers, heart attacks, strokes and diabetes worldwide, grouped together officially as non-communicable diseases, the World Obesity Federation (WOF) said in its estimates.
Globally, in 2016 an additional 213m young people were overweight although still below the threshold for obesity.
The analysis, led by Imperial College London in collaboration with the World Health Organization, involves data on almost 129 million children ages 5 to 19 in 200 countries.
Overall, 50 million girls and 74 million boys are now obese, which sets them up for serious health problems, the researchers said.
That's why the group wants to see health-care professionals trained to prevent and treat childhood obesity.
"But our data also shows 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".
The Lancet study also notes that despite these increases, there are still more children and adolescents who are moderately or severely underweight than are obese.
Among high-income countries, the United States had the highest obesity rates, where girls ranked 15th and boys ranked 12 worldwide.
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.
While obesity rates among young people in Europe and the U.S. were said to have plateaued, the authors stressed it was still a serious problem in these regions.
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The largest increase in the number of obese children and adolescents has been in East Asia.
There are now 10 times as many obese children and teens around the world than there were 40 years ago, and if current trends continue, there will soon be even more kids dangerously overweight than underweight, according to a new World Health Organization study. "Even though we may see some signs of improvement, we can not be complacent, and we need to ramp up our actions much more significantly to act across the life-course and across all of society", said Harry Rutter, a researcher at the London School of Hygiene and Tropical Medicine.
"This tells us something - industry can change", Prof Bull added. 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.
"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 said: "Don't be fooled by a report which initially would have you believe that child obesity levels have plateaued in the UK".
"What we have failed to do is to properly address obesity which is a great disgrace a great scandal".
"We have not become more weak-willed, lazy or greedy".
Dr Alison Tedstone, chief nutritionist at Public Health England, said: "Our sugar reduction programme and the government's sugar levy are world-leading, but this is just the beginning of a long journey to tackle the challenge of a generation".
"The evidence is clear that just telling people what to do won't work".