Intuitions about the causes of rising obesity are often wrong, researchers report

Everything you think you know about the causes of rising obesity in the U.S. might be wrong, researchers say in a new report.

Contrary to popular belief, people are exercising more today, have more leisure time and better access to fresh, affordable food - including fruits and vegetables - than they did in past decades. And while troubling disparities exist among various groups, most economic, educational, and racial or ethnic groups have seen their obesity levels rise at similar rates since the mid-1980s, the researchers report.

The new analysis appears in CA: Cancer Journal for Clinicians.

Obesity rates in the U.S. have been going up for decades, said University of Illinois kinesiology and community health professor Ruopeng An, who conducted the new analysis with Roland Sturm, of the RAND Corp. in Santa Monica, California.

"Many factors have been suggested as causes," the researchers wrote. Snack food, fast food, automobile use, time spent viewing television or looking at computer screens, the ubiquity of vending machines, suburban sprawl, increasing portion sizes, female labor force participation, poverty, affluence, supermarket availability and even the absence of supermarkets are blamed, the researchers said.

"As it turns out, some widely held beliefs about societal trends are unambiguously false; others require some qualifications," they wrote.

Obesity is more deadly than previously thought, but a nationwide survey shows that after rising for decades, rates have not increased for the first time in 30 years.

In the latest “F as in Fat” report, released annually by Trust for America’s Health and the Robert Wood Johnson Foundation, only one state, Arkansas, showed an increase in obesity rates while other states managed to keep their rates stable compared with the previous year. All of the 20 states with the highest obesity levels are located in the South or Midwest, with the exception of Pennsylvania. And for the first time in eight years, Mississippi is no longer the state with the highest adult obesity rate - Louisiana now holds that position with 34.7% of adults weighing in with a body mass index (BMI) above 30.

Once again, Colorado tops the list at the other end - as the state with the lowest obesity rate with 20.5% of its residents considered obese.

What helps Coloradans to stay at healthy weights, and what have states like Mississippi done to improve their standings? In Colorado, new laws require school districts to provide physical activity or recess during the day to help children burn off calories. That inspired other states - Arizona, Connecticut, Illinois, Indiana, Kentucky, Louisiana, Maine, North Carolina, North Dakota, Ohio and Tennessee - to pass similar laws.

Geography and the existence of so-called "food deserts" (neighborhoods or regions with limited access to affordable, healthy food) appear to have little bearing on the obesity trend in general, although they may be linked to differences between groups at any given point in time, An said.