(20-07-06) New foes in fight against fat

SAN JOSE, Calif. ? What do pollution, birth-control pills and air conditioners have in common?
Your expanding waistline, some scientists suggest.
In a new look at the causes of the nation's obesity epidemic, 20 researchers from eight states report that 10 often-overlooked factors could contribute to our growing girth. But proving that ? and doing something about it, if true ? will be another matter.
Pollution? It can disrupt the body's hormones and cause it to store more fat, they said.
Birth-control pills? Along with steroids, antidepressants and some other medications, they tend to promote weight gain.
Air conditioners? We burn more calories when we're hot, the scientists said, and tend to eat less then, too.
Even doing good may have a downside: Smokers tend to weigh less than nonsmokers. As smoking rates decline, the needle on the national scale creeps up. Sleep deprivation also is associated with increased appetite.
The study in Monday's International Journal of Obesity was praised by some who have long argued obesity is likely due to many factors. But it was criticized by others, who said it downplays the roles calorie consumption and exercise play.
"We are not saying for an instant that what you eat and how much energy you expend don't matter. They are the primary determinants of how fat one is," stressed David Allison, director of the University of Alabama, Birmingham's, Clinical Nutrition Research Center and one of the study's authors. "What we are saying is there are many influences on how fat one becomes."
During the past 20 years, obesity has become much more prevalent in the United States, with an estimated 30 percent of adults ? more than 60 million people ? now classified as obese, according to the Centers for Disease Control and Prevention.
Obesity is associated with an increased risk of a number of diseases, including type 2 diabetes, heart disease and some cancers.
As obesity rates soar, attention has been on snack foods and sodas and the lessening of physical activity.
But the study authors question whether that is shortsighted, possibly resulting in "well-intentioned but ill-founded proposals for reducing obesity rates" at a time all the causes aren't clear.
Many of the factors they cite in their report, a review of more than 100 obesity studies, aren't easy to control.
Children born to older mothers may be set up to be overweight. The same may be true if their grandmothers overate before giving birth, the researchers said.
The nation's aging population is also a factor, as well as larger populations of ethnic groups that are more prone to obesity.
Curvy, slightly overweight women tend to be more fertile than their string-bean-skinny counterparts and reproduce more, the study also explains, meaning future generations are more likely to inherit fat genes.
In addition, people are slightly more likely to choose mates of their own body style: thin with thin, rotund with rotund. Even though the effect is small, the scientists said, this could gradually skew society toward fatness.
"They left out global warming. I'm saying that in jest," said a skeptical Dr. Thomas Robinson, director of the Center for Healthy Weight at Lucile Packard Children's Hospital at Stanford University.
While Robinson said some explanations, such as sleep deprivation and smoking cessation, are plausible causes of weight gain, others may have little influence.
"These are really far-fetched explanations for something that's really simple: People are eating more and moving less," said Marion Nestle, professor of nutrition at New York University and author of "What to Eat."
The study doesn't attempt to address how much each of the 10 factors influences obesity, Allison said. Nor does it focus on all the possible causes. Working the swing shift and not breast-feeding have been implicated in some studies.
"We do not claim that all of the additional explanations definitely are contributors," the study authors wrote, but only that they are as plausible as diet and exercise "and deserve more attention and study."

By Julie Sevrens Lyons

Source: San Jose Mercury News

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