Children exposed to two chemicals which is prevalent in food packaging, are more likely to be obese or show signs of diabetes precursors than those with lower exposure levels, two studies published Monday suggest.

Two research articles published online August 19 in Pediatrics add to evidence that bisphenol A (BPA) and phthalates may be linked with increased health risks for children and adolescents.

Researchers found urine levels of one type of phthalate, used to soften plastic, were tied to a higher risk of insulin resistance among teenagers. Based on data from the same large nutrition survey, another study group linked bisphenol A, or BPA - used to line aluminum cans - to obesity and larger waists in youth.

One study, led by Dr. Leo Trasande, an associate professor of pediatrics and environmental medicine at the NYU School of Medicine, involved 766 adolescents aged 12 to 19 who were enrolled in a long-running study of their nutritional and dietary habits between 2003 to 2008.

"Clearly unhealthy diet and lack of physical activity are the drivers of this epidemic ... but increasingly environmental chemicals are being identified as possible contributors," said Dr. Trasande.

They found urinary levels of one particular type of phthalate, known as Di-2-ethylhexylphthalate (DEHP), were closely tied to a teenager's chance of having insulin resistance, a precursor to diabetes.  DEHP is often used to soften plastic bottles. It's used in plastic that is printed with the number 3 for recycling.

"There are lab studies suggesting these chemicals can influence how our bodies respond to glucose," Dr. Trasande noted. "In particular, they are thought to influence genes that regulate release of insulin. There are other potential mechanisms, but that is the main mechanism of concern."

In the other study, researchers Dr. Donna Eng and colleagues at the University of Michigan found that high urinary levels of BPA are associated with increased risk of obesity.

BPA is used to make polycarbonate and epoxy resins for a wide variety of products. For example, aluminum cans use a BPA lining to prevent corrosion. It has been linked to a wide variety of health concerns, and the U.S. Food and Drug Administration has banned its use in sippy cups, baby bottles and infant formula packaging.

"Although the evidence about BPA and adverse health effects are not definitive, as a clinician, I do recommend that parents try to avoid BPA-containing plastics when possible to minimize their family's exposure," the study's lead author, Dr. Joyce Lee, an associate professor of pediatric endocrinology at the University of Michigan in Ann Arbor, said to Reuters. "I also tell them to avoid microwaving food in plastic containers, as this can lead to chemicals leaking into the food."

However, the study only found an association and not a cause-and-effect relationship. Still, the researchers suggest parents and caretakers should switch to phthalate-free alternatives to food packaging such as wax paper and aluminum foil. Eating fresh foods that aren't canned or packaged may also reduce exposure.