IOM workshop examines role of environmental exposures in obesity epidemic
By Kelly Lenox
While exercising and healthy eating play crucial roles in the fight against obesity, current research is reshaping our understanding of the complex roots of this worrisome epidemic. The Institute of Medicine (IOM) Roundtable on Environmental Health Sciences, Research, and Medicine invited an international group of researchers to NIEHS March 2-3 to share their findings at “The Interplay Between Environmental Exposures and Obesity” workshop.
During his opening remarks, Frank Loy, chair of the IOM roundtable, noted that the research community focused on the issue reflects the multifaceted origins of obesity. “It involves an interplay between the public health community and those involved in environmental health,” he said.
Interaction of complex factors
Linda Birnbaum, Ph.D., director of NIEHS and the National Toxicology Program (NTP), elaborated on the workshop’s goals. “We want to try to tease apart that interaction [between genetic factors and environmental exposures], and to reinforce the concept that obesity, with its attendant comorbidities such as diabetes and metabolic syndrome, is a multifactorial outcome,” she said.
After emphasizing the overriding importance of nutrition and physical activity, Birnbaum posed the question presenters would shed light upon during the next two days. “We have to ask whether environmental chemicals are making it harder for us all to control our weight,” she said.
Broad scope and intriguing detail
Nearly 600 people registered for the webcast and about 120 attended in person, to hear researchers from academia, government, public health, and industry discuss the issue.
A theme Birnbaum expressed in her introduction was echoed throughout the presentations. “People and the problem continue to grow larger, and there is no single answer,” she said. Scientists shared work ranging from multigenerational studies of the effects of specific chemicals, to large-scale epidemiologic research and economic analyses (see text box).
For example, Kristina Rother, M.D., of the National Institute of Diabetes and Digestive and Kidney Diseases, discussed studies showing noncaloric sweeteners appear to increase insulin secretion and development of fat cells, and decrease the sense of reward. “There is no convincing evidence that artificial sweeteners prevent or alleviate obesity,” she said.
Obesity Society President Nikhil Dhurandhar, Ph.D., of Texas Tech University, shared research linking the adenovirus Ad36 with a greater potential for preadipose tissue to change into adipose tissue, or fat. One of several presenters participating by phone due to weather-related flight cancellations, he showed an intriguing series of maps in which the pattern of obesity increase in the U.S. resembled the spread of influenza, an infectious agent, more than it did the spread of asthma, a noninfectious disease.
Evidence linking perinatal bisphenol A (BPA) exposure in mice to increases in inflammation and systemic insulin resistance was shared by Beverly Rubin, Ph.D., of Tufts University. “It is very clear [from these and other studies] that the low doses of bisphenol A are the effective ones, and once you get across a certain border there is no effect,” she said, responding to a question about larger doses. “This may explain the controversy in the literature,” Rubin observed.
Each session included ample discussion time, during which audience members and online participants raised a wide range of issues, such as neurological factors that affect appetite and activity, changes in the composition of meat and produce over the past 50 years, and decreases in sleep duration.
Many speakers echoed a familiar refrain — the traditional focus on energy balance, or comparing calories consumed against energy burned, explains only part of the obesity epidemic.
The workshop concluded with far-reaching discussions of research needs and policy solutions. In closing, Loy praised the character and quality of the conversation throughout the workshop, reiterating that the event was meant to share information rather than reach a consensus.
Presenters’ slides and a video recording from the workshop are available on the IOM website. A workshop summary will be published later in 2015.
1. Framing the problem — Public and environmental health overviews highlighted the multiple pathways involved in the risk of obesity.
2. Life span view — Focusing on chemical exposures from pregnancy through adulthood, speakers addressed effects of prenatal and early life exposures to endocrine disrupting chemicals, as well as links between exposures, the onset of puberty, and obesity.
3. Biologic pathways — Scientists presented approaches to uncovering how environmental chemicals may disturb biologic pathways, including high throughput screening, studies of adipose tissue function and inflammation, and effects of environmental chemicals on energy metabolism and insulin secretion.
4. Nutrients, food additives, and antibiotics — Researchers shared their latest findings on the role of infectious agents, antibiotics, and food ingredients in the development of obesity.
5. Research needs and policy solutions — Presenters and the audience engaged in open discussion of new research directions and policies that might reduce exposure to chemicals associated with obesity.