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BPA may boost obesity in kids, study finds

Studies suggest that a chemical used to prevent corrosion in the lining of cans and bottles can make fat cells bigger, and disrupt the balance of estrogen and testosterone in our bodies. NBC's Dr. Nancy Snyderman reports.

Parents may have another reason to avoid bisphenol A, or BPA, the estrogen-like chemical found in many plastic bottles and cans. BPA may be making our kids fat, new research suggests.

In a nationally representative study of nearly 3,000 children and teens, researchers found that kids with the highest levels of BPA in their urine were 2.6 times more likely to be obese compared to those with low levels of the chemical. The report was published in the latest issue of the Journal of the American Medical Association.

It’s the latest evidence that obesity might be affected by more than just diet and exercise, said Dr. Leonardo Trasande, a professor of pediatrics and environmental medicine at the New York University School of Medicine.

“Clearly poor diet and lack of physical activity contribute to increased fat mass, but the story doesn’t end there,” he said.

The link was statistically significant only for white children and adolescents, who made up 62 percent of the study participants, researchers said. Connections between the highest levels of BPA and obesity weren’t found in black or Hispanic youngsters. Researchers said that link would need more study. 

Perhaps one of the most striking findings was that the association between BPA and obesity extended even to children who were consuming the right amount of calories.  

“We found that BPA in a child’s urine was associated with the chance of being obese, whether they were eating too many calories for their age and gender, or not,” said Trasande. “Our hypothesis is that something happens to the kids’ metabolisms.”

No one knows exactly what that might be, but experimental studies have shown that BPA can make fat cells bigger, Trasande said. The chemical also has been shown to inhibit a hormone called adiponectin, which is involved in lowering heart disease risk. And, because BPA is actually a weak synthetic estrogen, the chemical may disrupt the balance of estrogen and testosterone, which may adversely affect caloric balance.  

BPA exposure in the U.S. is “nearly ubiquitous,” the researchers said. Nearly 93 percent of people aged 6 or older had detectable levels of BPA in their urine, according to a 2003-2004 National Health and Nutrition Examination Survey. About 99 percent of that exposure comes from dietary sources.

Currently most of the BPA exposure is from canned goods. The chemical is in the resins that manufacturers use to coat the insides of cans to block metals from leaching into foods as well as to prevent a metallic taste.

Many plastic bottle manufacturers voluntarily changed their formulations to exclude BPA after the chemical was linked in animal studies to a host of health ills, including possible developmental problems. 

While the Food and Drug Administration has barred the use of the chemical in baby bottles and children’s sippy cups, the agency isn’t yet convinced that BPA must be completely banned. The FDA called for more research because, officials said, it has “some concern about the potential effects of BPA on the brain, behavior and prostate glands of fetuses, infants, and children.”

Trasande hopes his study will help.

“The FDA decided to take a wait-and-see approach, specifically looking for more evidence regarding the potential health consequences of exposure,” he said. “We believe this study provides critical information that the FDA needs to consider as they evaluate the need and the risk involved with keeping BPA in food products.”

Experts not affiliated with the new research said the new study was carefully done.

“This is an important study, albeit just one study,” said Dr. Richard J. Jackson, professor and chair of environmental health science at the Fielding School of Public Health at the University of California, Los Angeles. “We must pay attention to environmental chemicals that meddle with metabolism.”

Dr. Elizabeth Proutparks, an expert in childhood obesity, agreed that the study was very well done, but cautioned that more research must be conducted before anyone can say for certain that BPA actually causes obesity.

Proutparks was also concerned that parents might see this study and skip canned fruits and vegetables altogether.

“I don’t think I would tell them not to eat canned foods and vegetables,” said Proutparks, a nutritionist and attending physician with the healthy weight program at the Children’s Hospital of Pennsylvania. “You’d be limiting these foods in low-income populations, who already have issues as it is.”

Proutparks did advise parents not to re-use water bottles that contained BPA, noting that obesity isn’t the most worrisome possible side effect from the chemical. The most concerning effects would be on the developing brains of fetuses and infants, she said.

“I think there are other studies and other reasons to look for bottles that don’t have BPA in them,” Proutparks said. “But we need to put it all in perspective.”

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Researchers at the Harvard School of Public Health found that eating canned soup boosts urine concentration of the chemical bisphenol A (BPA) in humans. BPA is raising concerns among some health experts for its potential health effects in children, infants and fetuses. NBC's Robert Bazell has more.