May 17, 2016

expert reaction to bisphenol-A and obesity

A study published in the journal Environmental Health Perspectives has examined exposure to bisphenol-A in the womb and early childhood and report an association with increased weight at age 7.

Prof. Sir Stephen O’Rahilly MD FRS FMedSci, Professor of Clinical Biochemistry and Medicine and Director of the Metabolic Research Laboratories, University of Cambridge, said:

“The findings of this very small study are highly preliminary and should not influence public health policy. The hypothesis that BPA exposure during pregnancy predisposes to childhood obesity needs to be tested more rigorously in samples from considerably larger studies.”

Prof. Richard Sharpe, Group Leader of the Male Reproductive Health Research Team, University of Edinburgh, said:

“This is an association study, it does not show or prove cause and effect of maternal BPA exposure. There have been a number of similar studies of maternal BPA exposure and its effects on children, but the results are inconsistent in what they show.

“More than 95% of BPA exposure comes from our diet and some (but not all) studies have shown that eating a modern fast food diet increases BPA exposure. But crucially, over-consumption of a modern fast food diet clearly causes obesity. We know that maternal obesity increases the risk of child obesity, whether through effects on the fetus or because of shared diet. It is extremely difficult to control for this hugely confounding factor – most studies try to control for maternal BMI but controlling for specific dietary factors is rarely if ever done.

“What is the supposed mechanism for this effect?  The BPA exposure is extremely low and at such exposure levels there is no identified mechanism for its supposed effect on the developing fetus. BPA is an endocrine-active (weakly oestrogenic) chemical but its potency is over a million-fold less than the pregnancy oestrogens that circulate to the fetus during normal pregnancy, so the BPA is a drop in the ocean compared with this.

“Therefore, apply the common-sense factor. What causes obesity? Consuming too many calories. So which is more likely to be the culprit, eating/diet or BPA exposure? Just ask any member of the public to make their own mind up.”

‘Bisphenol A and Adiposity in an Inner-City Birth Cohort’ by Lori Hoepner et al. is published in Environmental Health Perspectives. 

Declared interests

Prof. O’Rahilly: I consult with Pfizer AZ and Medimmune in the area of drug development for treatment of metabolic diseases including diabetes and obesity.  I am president of the Society for Endocrinology. Grant funding from MRC, Wellcome Trust, EU and NIHR.