It's no secret that along with fast food and other trappings of convenience, unhealthy lifestyles—and their associated health problems—have been spreading across the globe at a rapid clip. A new analysis of more than nine million people in 199 countries and territories puts numbers on the widespread weight gain

Nearly half a billion adults were obese as of 2008, according to the analysis, published online February 3 in The Lancet. That is nearly double the 1980 rate, with an average increase in body mass indexes (BMIs) of 0.4 (kilograms per meter of height squared) each decade, reaching 23.8 in 2008. Some countries, especially those in Oceana, saw BMIs balloon up by some 1.3. A BMI of 30 or above is considered obese, and those with BMIs of 25 to 29.9 are overweight. Excess body weight is blamed for almost three million deaths each year internationally. 

"Obesity, high blood pressure and high cholesterol are no longer Western problems or problems of wealthy nations," senior study author Majid Ezzati, of Imperial College London's School of Public Health, said in a prepared statement. "Their presence has shifted toward low and middle income countries, making them global problems."

The U.S., where 34 percent of the adult population is overweight, leads the pack of high-income countries with the highest average BMI (more than 28 for both men and women) and the largest average BMI increase per decade: 1.1. Japan has the lowest average adult BMI of wealthy countries (with about 24 for men and 22 for women).

As the U.S. and other wealthy countries are continuing to tip the scales to higher and higher weight classes, BMI has not been creeping up everywhere in recent decades. Some places where getting adequate calories each day is still a concern saw an average drop in average BMI of 0.2 each decade. This is of particular concern for women, as low maternal BMIs put babies at higher risk of dying—especially in developing countries. But, the researchers found, in regions, such as sub-Saharan Africa and some parts of Asia, where average female BMI in 1980 was underweight (less than 18.5), the lowest national female average in 2008 was a healthy 21.

Global data on cholesterol and blood pressure—together still responsible for at least 11.4 million deaths each year—tell a slightly different story. Worldwide, cholesterol fluctuated little between 1980 and 2008 in adults 25 years and older, lingering around 4.7 millimoles per liter, according to a related Lancet study of three million people. Systolic blood pressure decreased slightly during the same study period (by 1 millimeters of mercury each decade to reach about 126 mm Hg in 2008), according to a third Lancet paper that analyzed data from 5.4 million people.

Although people in the U.S. and other Western countries still have the highest average cholesterol levels in the world, they have been dialing it—and blood pressure rates—down in recent decades thanks to improved screening and better medical management. Middle- and low-income regions tended to have the highest blood pressure, suggesting that more targeted interventions, such as improved screening and medical management, are needed there.

Growing awareness of the importance of a healthful diet, too, has likely played a role in starting to get these national numbers under control in wealthier nations. As highlighted by the recently released Dietary Guidelines for Americans, it is important to "implement policies that lead to healthier diets, especially lower salt intake, at all levels of economic development," Ezzati said.

These big three conditions are not the only lifestyle-linked diseases that have been exported from the U.S. Cancer deaths are predicted to surge in Asia, Africa and Latin America in the next decade, thanks in large part to changes in lifestyle, such as poor diet and tobacco use.

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