8 June 2009
Is the Environment Making Us Fat and Sick?
Conventional wisdom says that the meteoric rise in obesity and related health conditions – the early stages of which are now called metabolic syndrome – is due to the West having a bad case of “couch potato syndrome.” That is, over the past few decades, we have been eating too much and not exercising enough.
While poor diet and inactivity play an undeniable role in fostering metabolic syndrome, that’s not the whole story. Clinical and epidemiological evidence increasingly implicates another culprit: the environment.
An insufficient explanation
Some scientists suspect that a combination of environmental factors, including a group of chemicals called obesogens, share the blame for the explosion of metabolic syndrome and its later stages: diabetes, obesity, cardiovascular disease, and even Alzheimer’s.
“Despite what we’ve heard,” said Dr. Bruce Blumberg, Professor of Developmental and Cell Biology and Pharmaceutical Sciences at the Univeristy of California, Irvine, “diet and exercise alone are insufficient to explain the obesity epidemic.”
A May 7 teleconference presented by the nonprofit Collaborative on Health and the Environment explored this urgent and compelling topic. This article is based upon that teleconference.
Metabolic syndrome is estimated to affect more than one-third of U.S. adults, 60% of them under 65 years old.
When environment collides with human biology
Speaker Dr. David Jacobs, Professor of Public Health at the University of Minnesota, a chronic-disease epidemiologist, defined metabolic syndrome as “a constellation of related metabolic abnormalities (body fatness, blood fat handling, insulin, glucose).”
Environmental factors suspected to contribute to metabolic syndrome include the food system, the transportation system, the built environment, air pollution, obesogens, other environmental contaminants, and socioeconomic stress.
These stressors alter pathways in the body, causing inflammation, oxidative stress, and disrupted insulin signaling. Altered pathways can, in turn, lead to diabetes, obesity, cardiovascular disease, and abnormal lipids (tied to dementia and Alzheimer’s).
You can think of metabolic syndrome as a crossroads, said speaker Dr. Jill Stein, co-founder of the Massachusetts Coalition for Healthy Communities, board member of Greater Boston Physicians for Social Responsibility, and co-author of the recent report Environmental Threats to Healthy Aging (www.agehealthy.org).
“This is where the environment meets human biology in the early stages of the disease process. You can think of environmental factors as kind of colliding with human biology here."
The obesity epidemic, as Dr. Bruce Blumberg pointed out, roughly correlates with the rise in the use of industrial chemicals (plastics, pesticides, etc.) in the years since World War Two.
Though, he reminded listeners, “correlation is not causation."
Also, many environmental contaminants affect the endocrine system, which plays a big part in determining weight by controlling the appetite and metabolism, fat cell development, and lipid balance. These basic facts, plus suggestive laboratory research, has led scientists to propose an additional label for certain chemicals: obesogen.
Some time ago, Dr. Blumberg and his colleagues proposed “the obesogen hypothesis,” which defined obesogens as “chemicals that inappropriately stimulate adipogenesis and fat storage, exist and contribute to the obesity epidemic.”
Varioius studies have found that pre- and post-natal exposure to obesogens reprograms the metabolism of exposed animals, predisposing them to obesity later in life.
Dr. Pete Myers, founder, CEO, and chief scientist of Environmental Health Sciences, began the teleconference by describing one such study, by Soo Lim et al., published in the journal PLoS One in April 2009.
You can access the study at www.plosone.org/article/info:doi/10.1371/journal.pone.0005186