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Shortly after a study linked pre-natal exposure to bisphenol A (BPA) with an increased risk of undescended testicles in newborn boys, new evidence that highlights other potential adverse effects of the chemical has been presented. New research published in the journal PLOS ONE found that girls aged between nine and 12 that had high levels of BPA in their bodies were twice as likely to be obese as their peers. These findings were in line with previous animal studies that had established a link between exposure to BPA and obesity, explained Kimberly Gray, a health scientist at the National Institute of Environmental Health Sciences.

BPA is a chemical that is widely used in many consumer products, including plastic bottles and food packaging. The study found that the chemical is able to change the body's metabolism and to prevent weight loss, researchers noted.

For their research, the team of scientists examined urine samples of 1,326 children, both male and female, from fourth to 12th grade in three different schools. When assessing the influence of BPA, researchers also took into account various individual obesity risk factors, such as family history, diet, mental health and physical activity.

Analysis of the samples revealed that for girls aged between nine and 12 with a BPA concentration level of two micrograms per liter or more the risk was double, compared to girls with lower levels of BPA detected. Those who had extremely high concentration of BPA, over 10 micrograms per liter, were actually five times more likely to be obese.

Results from the research show that obesity is not simply about calorie intake and lack of physical activity. There are certainly other factors that play a part, said Bruce Blumberg, a professor of pharmaceutical sciences at the University of California, Irvine, who was not involved in the study.

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However, there was no link established between the concentration of BPA in girls older than 12 and in boys of all ages. According to lead researcher De-Kun Li, girls at puberty age could be more vulnerable to BPA exposure and the chemical's impact on their metabolism could be stronger. Li pointed out that researchers now plan to examine BPA exposure in the womb.

Some researchers noted that this may be a classic example of a vicious circle. BPA is easily absorbed in fatty tissue, so in fact obese children may be more prone to secreting the chemical, John Meeker, associate professor of environmental health science at the University of Michigan told USA Today.

However, Li argued that this was not likely because, if it were true, all obese children, regardless of their gender or age, would have high BPA levels and the study showed that that was the case.

The U.S. Food and Drug Administration (FDA) classes low exposure levels to BPA in food packaging as safe but the agency will review the study to make sure that all evidence relating to its safety has been examined, stated FDA spokeswoman Theresa Eisenman.