Do Plastics Cause Obesity, Too?
The evidence keeps mounting that chemicals may be playing a role in the obesity epidemic.
The obesity epidemic? Isn't obesity caused by eating too much and not exercising enough? Well, yes. But a growing body of evidence suggests a role for some chemicals, including bisphenol A or BPA . That's the stuff found in all sorts of plastics, including those used to make some baby bottles.
At an international meeting on obesity in Geneva yesterday, scientists from several countries, including the United States, Spain and Switzerland, presented the results of their latest research. The findings, all from studies on mice, showed that animals exposed to several chemicals, including BPA, just before or after birth, had a higher risk for obesity in adolescence or adulthood.
The theory is that these chemicals are "endocrine disruptors" -- meaning they mess with the hormonal system. Scientists suspect that these substances may set the metabolism on a path to obesity. Bruce Blumberg of the University of California at Irvine, has coined a term for these chemicals -- "obesogens."
At the European Congress on Obesity, Blumberg joined researchers from the National Institute of Environmental Health , the Environmental Pretection Agency, Tufts University and elsewhere to share the findings of their latest studies. In addition to BPA, researchers found such "obesogenic" effects in several chemicals, including tributylin, a compound in paint that is used on the bottom of boats and that shows up in shellfish, and PFOA, a compound used in the lining of popcorn bags, pizza boxes, Teflon and other household products.
Even at levels considered safe, the chemicals seemed to promote fat. Researchers are just starting to explore the mechanisms by which this might occur, but the plastics compounds seem to affect molecular switches involved in regulating the metabolism. Some of the studies found the chemicals appear to affect how insulin works, increasing the risk for diabetes.
Clearly, eating too much and exercising too little is the major cause of the obesity epidemic. And so far, evidence that chemicals may contribute to obesity comes from studies of on mice and rats, not people. So the link remains far from proven. But the findings are so consistent that scientists say we should pay more attention.
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