NEW YORK — A provocative new study suggests a connection between the BPA chemical used in food packaging and childhood obesity, but the researchers say their findings don’t prove it’s the cause.

While most people have traces of the plastics chemical in their bodies, the study found that children with the highest levels in their urine were twice as likely to be obese as those with the lowest. There are other factors that could explain the results, and many reasons why children gain too much weight, the researchers said.

“Clearly unhealthy diet and poor physical activity are the leading factors contributing to obesity in the United States, especially in children,” said lead author Dr. Leonardo Trasande of New York University.

But the study does hint that causes of childhood obesity may be more complicated, he added. He said it is the first national research to tie a chemical from the environment to childhood obesity, and seems to echo what some studies have seen in adults.

One puzzling result: Significant differences were detected only in white children. For black and Hispanic kids, obesity rates were similar for those with the lowest levels of BPA as those with the largest amount. The researchers couldn’t explain that finding.

The study was released Tuesday and is in Wednesday’s issue of the Journal of the American Medical Association.

The American Chemistry Council, which represents chemical manufacturers, called the study speculative and noted lab animal studies that found no evidence that BPA causes obesity.

“Attempts to link our national obesity problem to minute exposures to chemicals found in common, everyday products are a distraction from the real efforts under way to address this important national health issue,” the organization said in a statement.