Kim Painter

Special for USA TODAY

By sheer numbers, the USA handily leads the world in obesity, with 87 million of the world's 671 million obese people — 13% of the total for a country with 5% of the population, a new report says.

But we are hardly alone in our battle with bulges: Obesity is a growing problem worldwide and, by proportion, is even worse in some other countries, says the study to be published Thursday in the medical journal Lancet. Rates are rising among men, women and children, in rich countries and in poor countries, the report says.

"It's going up everywhere," says study co-author Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington-Seattle.

The new 188-country study is the most comprehensive look at obesity worldwide over the past several decades, and it paints a discouraging picture, Murray says: "The most concerning thing is that there's not a single country that has seen a decline in obesity in the past thirty years. … We hoped there would be some examples of success that you could latch onto. But there's a complete lack of success stories in bringing down obesity."

Obesity is more common in developed countries than in poorer nations, but it is rising in both, the report says. Throughout the world – including in the USA – obesity co-exists with pockets of hunger, Murray says.

Among the details:

•The number of overweight or obese individuals worldwide increased from 857 million in 1980 to 2.1 billion in 2013. That's nearly 30% of the world's population, up from about 20%.

•About one-third of adults in the USA are overweight (with a body mass index of 25 or above), and another third are obese (with a body mass index of 30 or above), as has been reported by the Centers for Disease Control and Prevention.

•Obesity rates are even higher in some countries, exceeding 50% among men in Tonga and among women in Kuwait, Kiribati, Micronesia, Libya, Qatar, Samoa and Tonga. "Those are extraordinary levels," Murray says.

•About 22% of girls and 24% of boys in developed countries are overweight or obese. So are 13% of boys and girls in developing countries.

•In the USA and other developed countries, increases in obesity have slowed; in developing countries, rates are accelerating.

The new study does not examine causes but lists possibilities, including increased calorie intake, changes in diet composition, decreased physical activity and even changes in the mix of bacteria that live in human guts in the modern world.

The report notes that population-wide weight gains and income gains generally go hand in hand around the world.

That seems to support a theory, advanced by another recent study, that a major cause of obesity is that food has become cheap relative to income.

"It's not just cheaper in terms of money. It's also more accessible and more available all the time in the form of prepackaged junky food that is not necessarily conducive to health," says Roland Sturm, a senior economist at RAND and co-author of that study, published last week in CA: Cancer Journal for Clinicians.

"It's a good thing that hunger has decreased," Sturm says, "but now we have to deal with another health issue."

This month, the World Health Organization launched a commission to study rising obesity among children worldwide and suggest solutions. A report is due in early 2015.