Over the past four decades, many countries underwent a "nutrition transition" as their economies grew, explained Hu. In those countries, such as India and China, people on the higher socioeconomic end of the spectrum became obese, he said, while people on the spectrum's lower end were underweight -- at first.
"But when countries become more wealthy, the trends become reversed," with the poorer population having access to cheaper, unhealthy foods and richer populations opting for healthier items, said Hu.
"There is a continued need for policies that enhance food security in low-income countries and households, especially in South Asia," said Ezzati. "But, our data also show 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."
We need a healthy transition, Ezzati said.
Experts believe countries therefore need to prioritize both problems, which they have not done to date.
"Our findings highlight the disconnect between the global dialogue on overweight and obesity, which has largely overlooked the remaining under-nutrition burden, and the initiatives and donors focusing on under-nutrition that have paid little attention to the looming burden of overweight and obesity," said Ezzati.
"If programs have always targeted getting more calories into children, they're not prepared when obesity hits, he said.
"Whoever is to blame for this epidemic, it's not the children," Waqanivalu said, adding that governments have created environments in which parents and children are surrounded by unhealthy food options and inadequate options for physical exercise.
"(Children) don't have much say in the environment they are brought up in," he said. "Parents only respond to the environment being created. The government determines the environment."
Putting solutions in place
"This data is stating what we have already said, but now quantifying the magnitude of the problem," said Waqanivalu. "By releasing (the data), we hope to generate more political action from countries."
Waqanivalu went on to explain there are proven measures that work to reduce obesity rates, such as sugar taxes, restricting marketing of unhealthy foods to children and policies to increase physical activity at schools.
"It's our hope that countries will see how big the problem is (in their population), know the solution and be able to take some steps," said Waqanivalu.
"This study is an important wake-up call for countries where childhood obesity if increasing rapidly, especially in parts of Asia where the economy is still developing quickly and the prevalence of childhood obesity is rising," said Hu whose own work has explored the rise in obesity rates in China and India.
"Dietary patterns are changing rapidly and accelerating obesity ... and will lead to chronicdisease down the road," said Hu.
Along with undernutrition, "we should be vigilant about both problems."