Common Beliefs About Obesity Could Be Wrong

By Jane Farrell

Why do we have an obesity epidemic? Experts have come up with a number of reasons, and most of them might be wrong, according to new research.

The findings, by investigators from the University of Illinois, Champaign, indicate that people have better access to fresh, affordable food than they did years ago. They also appear to be exercising more these days.
It’s true that sharp differences in obesity rates exist among various socioeconomic classes, but most classes have seen obesity rates rise at similar rates since the mid-1980s, the research found.

Ruopeng An, professor of kinesiology and community health professor at UI Champaign, led the analysis with Roland Sturm, of the RAND Corp., Santa Monica, California.

An said that looking at long-term trends can help experts better understand the obesity epidemic.

“Many factors have been suggested as causes,” the researchers wrote. Among the suggested reasons for the obesity epidemic: snack food, fast food, automobile use, time spent viewing television or looking at computer screens, increasing portion sizes, supermarket availability and (on the other hand) the absence of supermarkets.

But perhaps the most overlooked factor in the obesity discussion is that the rates are increasing across all socioeconomic groups. “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,” An 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…the obesity trend is for all groups.”

An said that a look at graphs of obesity over time, measuring weight gain by the increase in body mass index (BMI) reveals a more universal view. Blacks have a higher obesity rate than whites, but the obesity rate increase is almost the same over time. This is also true, he said, for people who didn’t graduate high school versus people who have college degrees, or lower-income people versus those with higher incomes.

“The gap between groups is secondary to the increase that all groups experience over time,” he said. “So a reversal of the obesity epidemic would need universal intuitions rather than a focus on certain groups.”

Another commonly offered explanation is that healthy food has become more expensive. But the research found that the cost of fruits and vegetables has dropped more than 20 percent since 1970. However, the price of fast food has dropped even more. The accessibility and affordability of fast food could be a crucial factor in the rise of obesity.

As for time spent in exercise, Americans in the Behavioral Risk Factor Survey reported in 2012 that they were exercising four more minutes per day than reported in 2003. However, they also reported sleeping an average of 10 minutes longer and watching 15 more minutes of TV.

The researchers said their findings indicated that the rise in obesity isn’t as simple as widely held beliefs have indicated. But the real reasons for the epidemic remain unknown

“We are kind of in a dilemma trying to figure out what really contributes to the obesity epidemic,” An said. “We have a lot of hypotheses but we really don’t have much data to support them at this stage.”
The new analysis appears in CA: Cancer Journal for Clinicians.