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Fetal Exposure to Common Chemicals Can Activate Obesity

Exposure to environmental chemicals found in everyday plastics and pesticides while in the womb may make a person more prone to obesity later in life, new research indicates.

20.02.2007 |Sascha Gabizon

SAN FRANCISCO, California, February 16, 2007 (ENS)
Obesity is generally discussed in terms of caloric intake - how much a person eats - and energy output - how much a person exercises.

But now Frederick vom Saal, professor of biological sciences in University of Missouri-Columbia's College of Arts and Science, has found that when fetuses are exposed to these chemicals, the way their genes function may be altered to make them more prone to obesity and disease.

Vom Saal presented his research today at the annual meeting of the American Association for the Advancement of Science, AAAS, in San Francisco.

"Certain environmental substances called endocrine-disrupting chemicals can change the functioning of a fetus’s genes, altering a baby’s metabolic system and predisposing him or her to obesity," said vom Saal.

"This individual could eat the same thing and exercise the same amount as someone with a normal metabolic system, but he or she would become obese, while the other person remained thin," he said.

This is a serious problem because obesity puts people at risk for other problems, including cancer, diabetes, cardiovascular disease and hypertension.

Using lab mice, vom Saal has studied the effects of endocrine-disrupting chemicals, including bisphenol-A, which the city of San Francisco has banned in children's toys from December 1, 2006.

Some polymers used in dental fillings also contain bisphenol-A, while epoxy resins containing bisphenol-A are popular coatings for the inside of cans used for canning food.

Toymakers and other companies affected by the ban have sued to block enforcement of the San Francisco ordinance, saying their products have been used safely for decades.

But vom Saal found that bisphenol-A and other endocrine-disrupting chemicals cause mice to be born at very low birth weights and then gain abnormally large amounts of weight in a short period of time, more than doubling their body weight in just seven days.

Vom Saal followed the mice as they got older and found that these mice were obese throughout their lives.

 He says studies of low-birth-weight children have shown a similar overcompensation after birth, resulting in lifelong obesity.

"The babies are born with a low body weight and a metabolic system that’s been programmed for starvation. This is called a thrifty phenotype, a system designed to maximize the use of all food taken into the body," vom Saal said. "The problem comes when the baby isn’t born into a world of starvation, but into a world of fast food restaurants and fatty foods."

More research must be done to determine which chemicals cause this effect. According to vom Saal, about 1,000 of the 55,000 human-made chemicals in the world might fall into the category of endocrine disrupting.

These chemicals are found in common products, from plastic bottles and containers to pesticides and electronics.

"You inherit genes, but how those genes develop during your very early life also plays an important role in your propensity for obesity and disease. People who have abnormal metabolic systems have to live extremely different lifestyles in order to not be obese because their systems are malfunctioning," vom Saal said. "We need to figure out what we can do to understand and prevent this."

In the past 30 years, the prevalence of overweight and obesity has increased sharply for both adults and children in the United States, according to the Centers for Disease Control and Prevention, a federal agency. Between 1976–1980 and 2003–2004, the prevalence of obesity among adults aged 20–74 years increased from 15.0 percent to 32.9 percent.

This increase is not limited to adults, the agency reports. Among young people, the prevalence of overweight increased from 5.0 percent to 13.9 percent for those aged 2–5 years, 6.5 percent to 18.8 percent for those aged 6–11 years, and 5.0 percent to 17.4 percent for those aged 12–19 years.

Although one of the national health objectives for the year 2010 is to reduce the prevalence of obesity among adults to less than 15 percent, current data indicate that the situation is worsening rather than improving.

"Perinatal Programming of Obesity: Interaction of Nutrition and Environmental Exposures" is the title of vom Saal’s AAAS presentation.

Also presenting with vom Saal at the AAAS symposium are Reth Newbold of the National Institute of Environmental Health Sciences, Bruce Blumberg of the University of California-Irvine, George Corcoran of Wayne State University and James O’Callaghan of the National Institute for Occupational Safety and Health.