Since 1980, nearly a third of adults and a quarter of children today are overweight, according to a report that said no country has turned the tide of obesity.
Traditionally associated with an affluent lifestyle, the problem is expanding worldwide, with more than 62 percent of overweight people now in developing nations, said the report.
There are some 2.1 billion overweight or obese people in the world today -- up from 857 million 33 years earlier.
Among the most striking statistics: more than half the population of Tonga is now classified as obese -- a dangerous level of overweight -- as are more than 50 percent of women in Kuwait, Libya, Qatar and Samoa.
The United States also stands out with nearly 75 percent of men and 60 percent of women overweight or obese, according to the Global Burden of Disease Study published in The Lancet medical journal.
"Obesity is an issue affecting people of all ages and incomes, everywhere," said Christopher Murray, director of the University of Washington Institute for Health Metrics and Evaluation, who helped collate the data for the period 1980 to 2013.
"In the last three decades, not one country has achieved success in reducing obesity rates, and we expect obesity to rise steadily as incomes rise in low- and middle-income countries in particular, unless urgent steps are taken to address this public health crisis."
One is considered overweight with a weight-to-height (BMI) ratio of 25 or over, and obese from 30 upward.
A staggering 671 million people now fall within the obese category, said the study -- 78 million of them in the United States, which accounts for five percent of the world's population, but more than a tenth of its grossly overweight people.
China and India, with much larger populations, trailed 2nd and 3rd in the top 10 obese countries with 46 million and 30 million people respectively, followed by Russia, Brazil, Mexico, Egypt, Germany, Pakistan and Indonesia.
Overweight people are more prone to cardiovascular disease, cancer, diabetes, osteoarthritis and kidney disease, and the soaring numbers are placing a heavy burden on health care systems, said the study.
Excess body weight is estimated to have caused 3.4 million deaths in 2010, and previous research has warned that an unabated rise in obesity could start eating away at life expectancy.
The study, based on data from 188 countries, said the prevalence of obese and overweight adults grew by 28 percent worldwide, and by nearly 50 percent for children.
For men, the increase was from 29 to 37 percent, and for women from 30 to 38 percent of the population.
- Fat child, fat adult? -
The study authors expressed concern that nearly a quarter of kids in developed countries and 13 percent in developing ones were overweight or obese -- up from 16 percent and eight percent in 1980.
Thirteen percent of American children are obese, almost 30 percent if you include overweight -- up from 19 percent in 1980.
"Particularly high rates of child and adolescent obesity were seen in Middle Eastern and North African countries, notably among girls," the study authors noted.
Other regional differences included a slower rate of increase in developed countries, but fast expanding waistlines in the Middle East, North Africa, Central America and Pacific and Caribbean Islands -- regions where many countries' overweight rates exceed 44 percent.
Fast gains were measured in Britain and Australia.
Women are heavier in developing countries and men in developed ones, said the study.
The World Health Organisation aims to halt the rise in obesity by 2025, a target the study authors said appeared "very ambitious and unlikely to be attained without concerted action and further research".
One solution, said Klim McPherson from Oxford University, was to return to the BMI levels of 1980 -- which would mean an eight percent drop in consumption across the UK alone, at a cost to the food industry of some 8.7 billion pounds (11 billion euros) per year.
"The solution has to be mainly political," he wrote in a comment on the study.
"Where is the international will to act decisively in a way that might restrict economic growth in a competitive world, for the public's health? Nowhere yet."