News in Science

Obesity, BPA link tenuous say experts

Causal link? US scientists say they have established for the first time a link between overweight and obese children and a common chemical found in everyday consumer products such as steel cans.

The study found that in a sample of nearly 3000 children and adolescents those with a higher concentration of bisphenol A (BPA) had significantly increased odds of being obese.

However, critics of the study say that there is no causality shown in the study, which was led by Dr Leonardo Trasande of the New York University School of Medicine, and says the researchers themselves had acknowledged this.

The study, published in the Journal of the American Medical Association, says that of four groups of children, around 22 per cent of those with the highest level of BPA in their urine were obese, compared to 10 per cent among those with the lowest level of the chemical.

"To our knowledge, this is the first report of an association of an environmental chemical exposure with childhood obesity in a nationally representative sample," the study's authors write.

The American Chemistry Council dismisses the study as having "fundamental limitations," and labels it a "distraction from the real efforts under way to address this important national health issue."

"Due to inherent, fundamental limitations in this study, it is incapable of establishing any meaningful connection between BPA and obesity," the council says in a statement.

The industry group also noted that the study's authors acknowledged obesity was a condition that takes time to develop, and says it was inappropriate to link BPA exposure to obesity among people that already suffered from it.

Professor Ian Rae, an Honorary Professorial Fellow at the University of Melbourne, says the link between BPA and obesity is weak.

"Mere association is not sufficient evidence of causality, but it is a hint that there might be causality that deserves further investigation," says Rae. "However, appropriate investigations are extraordinarily difficult to design and carry out."

University of Adelaide researcher Dr Ian Musgrave says the link "may simply be a marker of food intake".

"The highest levels of BPA in the study are correlated with high calorie consumption (a known contributor to obesity)," he adds.

"While an interesting and careful study ... this paper does not provide evidence that current exposures to BPA will cause obesity."