GENEVA Exposure in the womb to common chemicals used to make everything from plastic bottles to pizza box liners may program a person to become obese later in life, U.S. researchers said on Wednesday.
Their studies of mice showed animals exposed to even tiny amounts of the chemicals during development were fatter when they grew older compared with mice not exposed to the compounds, they told the 2008 European Congress on Obesity.
"We are talking about an exposure at very low levels for a finite time during development," said Jerry Heindel of the U.S. National Institute of Environmental Health Sciences.
"The fact that it is such a sensitive period, it may be altering the tissue and making people more susceptible to obesity."
The World Health Organization estimates some 400 million people are obese, a problem that raises the risk of conditions like type 2 diabetes and heart disease.
Previous studies have linked these chemicals -- also found in water pipes -- to cancer and reproductive problems, prompting a number of countries and U.S. states to consider potential bans or limits of the compounds, the researchers said.
One of the chemicals is called Bisphenol A, found in polycarbonate plastics. Past research has suggested it leaches from plastic food and drink containers.
A team at Tufts University in the United States showed that female mice whose mothers were exposed to this chemical early in pregnancy gained more weight in adulthood even though they ate the same amount of food and were as active as other mice.
A similar effect occurred with perfluorooctanoic acid -- a greaseproofing agent used in products such as microwave popcorn bags. These animals were unusually small at birth then became overweight later in life.
"One of the problems we are finding is we don't know where all these chemicals are," said Suzanne Fenton, a research biologist at the U.S. Environmental Protection Agency, whose research focused on perfluorooctanoic acid.
The chemicals appear to disrupt the endocrine system by altering gene and metabolic function involved in weight gain, said Bruce Blumberg, a University of California biologist.
The result is the offspring store fat cells more efficiently, which makes them gain weight, he said. Blumberg studied tributylin, a chemical used in boat paint, plastic food wrap and as a fungicide on crops.
The findings suggest some people may be programmed to obesity before birth and underscore the need to identify biomarkers scientists can use to identify people at risk, the researchers said.
"We are calling this an emerging hypothesis," Heindel said. "Most of the data is in animals and we want to develop some biomarkers that could be used in humans.
(Editing by Matthew Jones)