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Melissa Lee | New University
Melissa Lee | New University
Bruce Blumberg’s study suggested that exposure to certain chemicals may influence obesity in humans.
The European Congress on Obesity met in Geneva on May 14 to present three studies conducted on animals, one of which was conducted by UC Irvine professor of developmental and cell biology Bruce Blumberg, which suggested that exposure to certain chemicals could affect obesity in humans.
Blumberg based part of his experiment on previous work done by some of his colleagues in Japan, who had exposed fishes and snails to the chemical tributylin. Tributylin is present in products such as baby bottles and plastic containers. They found that exposure to this chemical caused the sex of the animals to be manipulated in such a way that females would turn into males and vice versa. Since Blumberg was also testing hormone receptors at the time, he put tributylin on the top of his list and tested frogs, expecting similar results. However, instead of activating the receptor that produces sex hormones, the chemical unexpectedly activated the receptor PPR Gamma, which controls the production of fat cells.
Blumberg then continued his research by exposing pregnant mice to the same dose of tributylin found in humans and ended up the same results. Due to the exposure of this chemical, the fetus of these pregnant mice became predisposed to permanent changes in their genetic makeup. Fat cell production increased their appetite and they became prone to gain weight.
“Our work shows that prenatal exposure to tributylin predisposes the exposed animals to become overweight later in life, despite normal diet and exercise. Other labs have shown that bisphenol A, another common contaminant has the same effect. So the real concern here is that prenatal exposure has altered the epigenetic programming of the individual such that they are more prone to produce fat cells and fill these cells with fat than are non-exposed individuals. Therefore, while an exposed person is not doomed to become obese, it is more difficult to keep from gaining weight,” Blumberg said.
Although fourth-year English major Sara Thede was unaware of this new scientific finding, the young mother did not take this cautionary warning lightly.
“It is one more reason to feed my child natural and unpackaged healthy food,” Thede said.
Although the chemical has only been tested on animals thus far, Blumberg insists that it is very unlikely that the same results would not translate to humans. Since tributylin has the same type of receptors across different species, the effects should carry over.
Professor of medicine and director of the Joslin Diabetes Center at UCI, Ping Wang weighed in on the implications of the study.
“This study is done in animals, and the exact road of this compound on obesity has yet to be proven in humans. Nonetheless, these studies shed new light into the research area in obesity,” Wang said.
Second-year psychology and social behavior major Angie Cung agreed that there was a vital need for more studies that explored the topic of obesity.
“Obesity is a problem in America that needs to be tackled with some kind of solution to prevent this. There definitely needs to be more studies conducted and more research in this area because if what this study proposes is true, many people will be affected by obesity in the future since baby bottles are the main products used by parents,” Cung said.
Blumberg addressed that the toxicity of these chemicals could be prevented if the industry simply stopped using these chemicals in their products.
“Industry will always claim that such chemicals are safe and effective and that they can’t produce the products we need without them. Then, once the chemicals are banned or regulated, they quickly come up with substitutes and advertise the absence of the harmful chemicals,” Blumberg said.
Clinical professor Stanley Bassin elaborated that the industry not only catalyzes obesity through the toxicity of their storage products, but also through the calorie-dense foods they endorse.
“You have the behavioral perspective that it’s the environment that causes this obesity. … [The industry] creates a toxic environment through their marketing strategies that make certain types of food look very appealing. Obesity is, in part, a result of globalization. These products are sold internationally. I’ve done some work in New Zealand and have seen the same calorie-dense beverages sold there. The obesity issue is international, not localized,” Bassin said.
Bassin is currently a co-investigator for a study called “HEALTHY” that started in the fall of 2006 and is set to end in spring of 2009. It is currently the largest school-based study that the National Institute of Health has ever conducted. In this obesity study, researchers are trying to alleviate occurrences of type-II diabetes by changing the institutional culture of 40 middle schools across America. The students of these schools are currently being tested through changes in their food choices in cafeterias and increasing their physical expenditure in physical education classes. There are currently seven sites participating in the study, one of which includes UCI. Researchers are currently conducting their experiment in middle schools in the Long Beach Unified School District. The final data will be collected in March and April of 2009. Conclusions of this study will also follow soon thereafter.
Whether obesity is due to genetic manipulations, a society obsessed with excessive food consumption or a combination of both, it has nonetheless become a growing epidemic that has skyrocketed in the past 20 years. According to the World Health Organization, an estimated 700 million people will be obese by the year 2015.

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