Study links food-packaging chemical and obesity in girls

Unhealthy diets and limited physical activity are leading causes of obesity in children, and now new research adds to growing evidence that the chemical BPA found in food packaging may be partly to blame.

The study, published in the journal PLOS ONE, shows girls between ages 9 and 12 with high BPA levels had double the risk of being obese than girls with low BPA levels, validating previous animal and human studies, said Kimberly Gray, a health scientist at the National Institute of Environmental Health Sciences.

BPA, or bisphenol-A , is a chemical laced in everything from plastic bottles to metal food containers. The chemical can alter the body's metabolism and make it harder to lose weight, experts said.

The study by Kaiser Permanente draws on urine samples of 1,326 male and female children from fourth through 12th grades at three Shanghai schools. Researchers took into account common obesity risk factors, including diet, mental health, amount of physical activity, and family history.

Girls between ages 9 and 12 with high levels of BPA — 2 micrograms per liter or more — were two times more likely to be obese than girls with lower levels of BPA in the same age group. Girls with very high levels of BPA — more than 10 micrograms per liter — were five times more likely to be obese, the study shows.

"There's this dogma that weight is about calories simply going in and out. This research suggests that's simply not the case," said Bruce Blumberg, a professor of pharmaceutical sciences at the University of California, Irvine. Blumberg was not involved in the study.

Here's the catch: Researchers did not find any significant relationship between BPA and obesity levels in girls older than 12 and boys of all ages. Puberty-age girls could be more sensitive to the impact of BPA on metabolism, said lead researcher De-Kun Li.

"It's the proverbial chicken-egg scenario. We could be seeing the opposite trend at work," said Leonardo Trasande, associate professor of environmental medicine and pediatrics at New York University (NYU).

Because BPA easily absorbs into fatty tissue, children with obesity could also be more likely to secrete the chemical, said John Meeker, associate professor of environmental health science at the University of Michigan.

Li dismissed the claim, saying that if obese children secreted more BPA, obese children in all age groups would have high BPA levels and they didn't see that pattern.

The new study confirms a 2012 study by NYU researchers which found that more than 22% of kids and teens ages 6 to 19 with the highest BPA levels were obese. Kids and teens with low BPA levels had a 10% risk of obesity, according to the study, published in the Journal of the American Medical Association.

The Food and Drug Administration (FDA) maintains the safety of the low exposure levels of BPA in food packaging and will review the study to address BPA safety, said FDA spokesperson Theresa Eisenman.

"Attempts to link our national obesity problem to minute exposures to chemicals found in common, everyday products are a distraction from the real efforts underway to address this important national health issue," the American Chemistry Council, a major trade association, wrote in a statement.

Long-term, population-based studies that track BPA from the womb to early adulthood are required to confirm the relationship. Urine samples fail to measure BPA lodged in tissue and more specific measures of obesity and hormones are needed, Gray said.

Researchers of the new study plan to examine BPA exposure in the womb, Li said.

What's the takeaway? BPA exposure is nearly ubiquitous, said Philip Gruppuso, professor of pediatrics at Brown University. More than 92% of Americans older than age 6 have detectable levels of BPA in their body, the Centers for Disease Control and Prevention (CDC) says.

Gruppuso advises parents to limit use of food packaged in plastic and avoid heating infant formulas — but with a grain of salt.

"You can go crazy trying to think of all the things you might do to prevent exposure," he said. "Don't over-interpret the results. The major hazard may not be the plastic but the food the plastic is used to wrap up."