Obesogens

Is plastic making us fat?

Being fat has long been seen as a personal problem, fixed only by struggling against the proliferation of fast food restaurants, unlucky genes, and a sedentary life. Could something in the environment also be making people fat in epidemic numbers?

Animal studies in recent years raise the possibility that prenatal exposure to minuscule amounts of common chemicals - found in everything from baby bottles to toys - could predispose a body to a life of weight gain. The chemicals, known as endocrine disrupters, mimic natural hormones that help regulate, for example, how many fat cells a body makes and how much fat to store in them.

These findings have led some scientists to put forth a provocative argument: They say diet and too little exercise clearly are key reasons for the worldwide rise in obesity in the past 20 years, but they may not be the only ones. Food intake and exercise just haven't changed that much in that period, they argue. And while genetics obviously play a role - just think of someone you know who can eat three Big Macs a day and never gain an ounce - these researchers say it would be impossible to see such widespread genetic change in just two decades, giving them more reason to suspect the environment.

"This is a really new area . . . but from multiple labs on multiple levels we are getting preliminary data that all say the same thing: Chemicals can play a role," said Jerry Heindel, a program administrator for the National Institute of Environmental Health Sciences. "We know that nutrition and exercise are very, very important, but underlying that could be environmental exposures during development that alter your physiology, including how you respond to food and exercise."

Thousands of chemicals have come on the market in the past 30 years, and some of them are showing up in people's bodies in low levels. Scientists studying obesity are focusing on endocrine disrupters - which have already been linked to reproductive problems in animals and humans - because they have become so common in the environment and are known to affect fat cells.

A recent US Centers for Disease Control and Prevention study found that about 93 percent of the US population had bisphenol A, a chemical that can be found in canned goods and in hard, clear plastic items such as baby bottles and hiking containers, in their body. A study at the University of Missouri-Columbia showed that mice fed bisphenol A during early development - at lower amounts than what would have resulted in the levels found in most people in the CDC study - become markedly more obese as adults than those that weren't fed the chemical.

Bisphenol A is only one of the chemicals scientists are studying. Tributyltin, an endocrine disrupter that is used as an antifungal agent in agriculture and in marine paints to keep ship hulls free of barnacles, is also being studied. Female mollusks exposed to the chemical were seen to grow male sex organs. Lab mice exposed to tiny levels of tributyltin during prenatal development became fatter adults than those not given the chemical.

Scientists are focusing on early development because it is a critical time for determining a baby's long-term health and weight. For example, studies show that babies born underweight are likely to be fatter later in life, possibly because undernourished fetuses learn to use fat cells more efficiently - and it gets embedded in their physiology. Researchers suspect the same thing may be taking place with chemical exposures.

Growing up with more fat cells isn't necessarily a problem if you are running around a lot, but in a world where exercise is down and poor diets abound, it could exacerbate a weight problem.

There is evidence these chemicals have a multitude of deleterious effects in animals. . . We should be worried!

Any questions??