The Interplay Between Environmental Chemical Exposures and Obesity Proceedings of a Workshop (2016) / Chapter Skim
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2 Framing the Problem
2 Framing the Problem
Pages 5-20
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From page 5... ...
PUBLIC HEALTH OVERVIEW The first speaker was William Dietz, the director of the Sumner Redstone Global Center for Prevention and Wellness at the Milken Institute of Public Health at George Washington University. He presented his observations via the telephone.
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Thhere have beeen similar increases in obesity amoong children in countrries around thet world. The T worst prroblems havve been in tthe develooped world, but b even in developing ccountries thee prevalence of obesityy has been inncreasing, althhough the preevalence stilll remains muuch lower than that in thhe developed world.
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From page 7... ...
However, the change in the energy balance necessary to reduce obesity is much greater than that necessary to produce it. Physical activity can play a significant role in changing body composition, but it is a poor way to lose weight because it is hard to achieve the major caloric deficits necessary for weight loss through physical activity.
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From page 8... ...
In the 1950s, he said, the typical diet consisted of milk and other dairy products, meat and eggs, potatoes, fruits, and vegetables -- in short, mostly unprocessed foods that were prepared at home. Today, a much larger portion of the average American diet is highly processed: pizza, sodas, canned foods, and so on.
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Maternal behavioral factors associated with obesity in a child include a higher prepregnancy weight, excessive weight gain during pregnancy, gestational diabetes, and tobacco use during pregnancy. Finally, early exposure to various adverse experiences -- including physical and verbal abuse, family incarcerations, divorce, poverty, drug use, and alcohol use -- is associated with an increased prevalence of severe obesity in adulthood.
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From page 10... ...
A Brief History of the Field Heindel began by offering a brief history of the field of environmental exposures and obesity. The field got its start in 2002, he said, with a review article by Paula Baillie-Hamilton, "Chemical toxins: A hypothesis to explain the global obesity epidemic" (Baillie-Hamilton, 2002)
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From page 11... ...
In that search she identified a number of toxicological studies going back to the 1970s and 1980s that had shown that various chemicals increased weight in experimental subjects. The types of chemicals on her list included pesticides, such as organophosphates and carbamates; polychlorinated biphenyls (PCBs)
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From page 12... ...
The biggest change occurred in 2006, when Bruce Blumberg of the University of California, Irvine, wrote a review article and coined the term "obesogen,"1 Heindel said. "I think that really stimulated the field because it caught on in the press." In just the past few years, NIEHS has funded another initiative on the role of environmental chemicals in the development of obesity, type 2 diabetes, and the metabolic syndrome with the goal of stimulating new research in the field.
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From page 13... ...
He pointed out that although there are chemicals that will cause weight gain in adults, it is believed that the developmental stage is much more sensitive to metabolic disruptions and the development of obesity, and as a result, the field has been focused on developmental exposures to chemicals linked to an increased likelihood of obesity later in life. This is the obesogen hypothesis: that the obesity epidemic is due, in part, to environmental exposures during development.
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From page 14... ...
"It is very important that you all realize that we who are working in this field understand that food intake and exercise are very important and that they are certainly key to the obesity epidemic," Heindel said. "But we believe that environmental chemicals are altering the set point or sensitivity for gaining weight -- that is, how much food does it take to put on weight and how much exercise does it take to reduce weight.
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From page 15... ...
The lesson, Heindel said, is that the experimenter must pay attention to the effects of very low doses because in many cases the dose–response curves are not linear. In addition to animal models, Heindel said that about 33 human epidemiology studies have now linked developmental exposure to environmental chemicals to weight gains in children later in life.
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From page 16... ...
Heindel closed by noting that because the field is so new, there are many opportunities to help direct the research. That is why meetings like this workshop are so valuable, he said, so that it is sooner, rather than later, that the field is able to understand the importance of environmental chemicals in the obesity epidemic.
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Heindel answered that the fact that it takes only a small increase in calories to result in weight gain over time helps people to accept the idea that environmental chemicals can play a role. For the most part, he said, the effects of environmental chemicals are not large; they are just increasing the susceptibility or altering the set point.
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From page 18... ...
If environmental chemicals can perturb that process, then the end result will be some problem later on. As we move forward, we are certainly going to look at other windows of exposure." Barbara Corkey of Boston University commented that the epidemiological studies that had been discussed during the session could form the basis for some interesting hypotheses, but they did not actually prove causation.
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From page 19... ...
2002. Chemical toxins: A hypothesis to explain the global obesity epidemic.
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