Today the Arizona Daily Star published a special report about childhood obesity in Southern Arizona.

The problem is not just local.

To see how obesity has evolved in the United States, the U.S. Centers for Disease Control & Prevention has an illustrated history through maps.

It's dramatic to see the high obesity states begin as a smattering in the Southern states in the 1980s and then rapidly increase, to nearly cover the country by the 2000s.

There's only one state in the country - Colorado - that does not have an adult obesity rate of 20 percent or more.

But modern life is making people fat all over the world.  In Britan, two-thirds of adults are either overweight or obese.

Childhood obesity is a problem in Canada, Spain, Greece. Mexico and Italy.

Today's Star report correlates obesity with socioeconomics, which is consistent with the global problem.

 In  the 2009 book "The Spirit Level: Why Greater Equality Makes Societies Stronger,"   authors and epidemiologists Richard Wilkinson and Kate Pickett note that obesity levels are highest in countries with the biggest gaps between the rich and poor.

About 30 percent of U.S. adults are obese. Compare that to Japan, where only 2.4 percent of adults are obese. In Japan, income inequality is extremely low. In the U.S., it's extremely high when compared with other developed nations.

"It seems that people in more unequal societies are eating more and exercising less," the book says.

"Because behavior changes are easier for people who feel in control and in a good emotional state, lessening the burdens of inequality could make an important contribution towards resolving the epidemic of obesity."