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 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.
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.
"A common misbelief is that the obesity epidemic reflects increasing social disparities and that the largest weight gains are concentrated in groups identifiable by race, ethnicity, income, education or geography," he said. "And it's true that if you look at the national data for any one point in time, it's not hard to figure out, for example, that the people with the lowest education tend to have the highest obesity rate. Everyone buys this argument. But what is less obvious is how surprisingly similar the obesity trend is for all groups."