Girls ages 9-12 with higher levels of bisphenol-A in their urine had twice the risk of being obese than girls with lower BPA levels, U.S. researchers say. Principal investigator Dr. De-Kun Li, a reproductive and perinatal epidemiologist at the Kaiser Permanente Division of Research in Oakland, Calif., said BPA is used to make plastics and other materials, such as cash register receipts. It is a known as an endocrine disruptor and in children and adolescents, BPA is likely to enter the body primarily through the ingestion of foods and liquids, Li said. \"This study provides evidence from a human population that confirms the findings from animal studies -- that high BPA exposure levels could increase the risk of overweight or obesity,\" Li said in a statement. \"Girls in the midst of puberty may be more sensitive to the impacts of BPA on their energy balance and fat metabolism.\" The study was conducted in Shanghai as part of a larger national study of puberty and adolescent health. Li and colleagues studied 1,326 male and female children in grades 4-12 at three Shanghai schools -- one elementary, one middle and one high school. In addition to urine samples, the researchers obtained information on other risk factors for childhood obesity, such as dietary patterns, physical activity, mental health and family history. The study, published in the journal PLoS One, found girls with a higher-than-average level of BPA in urine -- 2 micrograms per liter or greater -- were associated with twice the risk of having a body weight in the top 10th percentile for girls of their age in the same population.