January 2013

Volume 22, Number 1

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Obesogens-A Fatty Issue

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A number of common substances can influence the development of fat cells and contribute to obesity.

Image: Beth Moore

While the obesity epidemic in the U.S. and other developed countries is often blamed on sedentary lifestyles and super-sized food portions, new research is pointing a finger at a class of chemicals dubbed obesogensendocrine disruptors that influence fat storage, metabolism, or appetite and are being found in a range of common substances, including building products and food.

The term was coined in 2006 by University of California–Irvine biologist Bruce Blumberg, who observed that mice given tributyltin (TBT, a biocide) during pregnancy gave birth to young that grew significantly heavier than non-exposed mice. Researchers found that the TBT had activated the receptors responsible for the creation of adipocytes, or fat cells, in the offspring—the same receptors that perform that role in humans. (Some pharmaceuticals are known to cause weight gain by activating the same receptors.) Adipocytes not only store energy but also produce hormones regulating appetite; extra adipocytes can lead to both increased hunger and increased fat storage.

TBT has been phased out of antifungal marine paint, but it is still used as a wood preservative and as a stabilizer in PVC, and a 2010 study found similar compounds in vinyl wallpaper and window blinds, self-stick urethane tile, and household dust. Phthalates, found in flexible PVC and other plastics, have also been linked to obesity and hormonal changes.

Bisphenol-A (BPA), used in epoxy resins for food-can linings and a wide range of coatings, has been found to have similar effects. In lab cultures, prefibroblasts that would normally become connective tissue turn into fat cells after exposure to BPA. In animal studies, BPA actually reduces the number of fat cells—but those that are created are larger. Rodents are affected by BPA at a relative dose 1,000 times lower than the dose presumed safe for humans; researchers speculate that receptors are fine-tuned to respond to very low levels of the body’s own hormones and so are susceptible to minute amounts from the environment. Most Americans have measurable levels of BPA in their bodies.

Conventionally grown fruits and vegetables are also a potential source of obesogens, with a number of pesticides linked to weight gain in children and animals. Food preparation can also add obesogens to the diet, as can interior building products: perfluorooctanoic acid (PFOA) and other compounds used in nonstick cookware and as waterproofing or stain repellents for carpets and textiles also activate the adipocyte-creating receptors. When PFOA was given to pregnant mice, it was later found to be present in the nursing mothers’ milk, continuing exposure beyond birth; the pups grew to be obese.

Diet and exercise are clearly essential in countering obesity, but individuals, designers, and manufacturers can take steps to reduce exposure to obesogen-containing materials like PVC and epoxies—possibly helping prevent a predisposition to obesity.

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December 31, 2012