You can scratch off the United States from the list of the world's fattest nations, according to an exhaustive country-by-country report on obesity published last week in The Lancet. We're not even in the top-10 anymore.

Truth be told, in all these years we thought we were the fattest, we really weren't. The United States was merely the most corpulent industrialized nation. The far fatter island nations of Nauru, Samoa and just about everywhere else in Oceania surpassed the U.S. obesity rate decades ago with the introduction of American favorites such as Spam and soda pop.

But move over, everybody, because here comes the Middle East. The fattest industrialized nation is now the United Arab Emirates, with an average body-mass index (BMI, or a calculation based on height and weight that estimates a person's fatness) of 28.9, followed closely by Qatar at 28.5.

The fattest of the fat

Those with a BMI over 25 are considered overweight; those with a BMI over 30 are considered obese. The average BMI in the United States is 28.4 — that's lower than Kuwait and Saudi Arabia (technically not industrialized nations) and the same as Egypt.

So, in the world ranking, the United States settles in at around number 20. The women save us: U.S. men are the 10th fattest, but U.S. women rank number 36 in BMI.

There's nothing to be proud about, though, according The Lancet study, led by researchers at Harvard School of Public Health and the World Health Organization. The United States isn't losing weight; the rest of the world is simply gaining weight at a faster pace.

We still are fatter than Mexico, with its average BMI of 28.1, but probably not for long.

Oceania, sadly, is the biggest mess, according to The Lancet report. The dubious honor of being the fattest nation goes to Nauru, whose people have an average BMI of 34.5. Nearly every single adult on this island is overweight, and over 80 percent are obese. The islands of the South Pacific dominate the top-10, and the majorities of these populations are diabetic. Their once healthy diet of fish and vegetables has been replaced nearly entirely by canned and processed foods.

Genetic connection?

Few countries have average BMIs in the healthy range of 20 to 25, The Lancet study reveals. This is seen only where people are starving, such as in Ethiopia (average BMI of 20.4), or where people eat a sensible diet dominated by vegetables, such as in Japan (average BMI of 22.7).

Asia, in fact, is the only region with the average BMIs below the overweight range. Much of South America has crossed into the 26 BMI range, and the average BMI in Europe and Australia is approaching 27. The United Kingdom is the fattest European country, with an average BMI of 27.1.

Still think the obesity epidemic has something to do with genetics? Perhaps. Genetic risk factors apparently include being African, Arabic, European, Eurasian, Pacific Islander, Native American, and Asian living outside of Asia.

For those who like to be number 1, remember that the United States still has the highest rates of teen pregnancy and homicide among industrialized nations. No one should be touching that record anytime soon. Go USA!

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on Live Science.