Obesity today affects about 42% of individuals in the United States, but there is no simple cause. After all, genetics, muscle mass, food, exercise habit, and environmental factors all have a role in a person’s weight. A new study, however, discovered a startling contributor to weight in women: air pollution.
The study, published in the American Diabetes Association journal Diabetes Care, examined data from 1,654 women from the Study of Women’s Health Across the Nation, a multi-site, long-term study meant to assess the health of women in their middle years. Body size and body composition data were acquired from the women, who had a median age of 49.6. The researchers also tracked annual exposure to air pollution.
What they discovered was that the more air pollution the women were exposed to, the higher their risk of acquiring obese. Air pollution was directly connected to increased body fat, a higher proportion of fat, and a lower lean body mass in middle-aged women. Women who were exposed to air pollution gained 4.5% more body fat or around 2.6 pounds.
The researchers also looked at how air pollution and physical activity affected body composition and discovered that high amounts of physical exercise were an effective approach to counterbalance air pollution exposure.
According to the study’s lead author, Xin Wang, a research investigator in the Department of Epidemiology at the University of Michigan School of Public Health, he and his team wanted to identify and study “modifiable risk factors, including exposures to environmental pollutants,” to help identify people who are at high risk for obesity.
It’s not unexpected, according to Wang, that air pollution may play a role in the development of obesity. “It is not difficult to establish in history that the rapid growth in obesity prevalence has accompanied the rising exposure to environmental contaminants,” he says.
Wang points out that studies have already connected exposure to air pollution, including fine particulate matter, nitrogen dioxide, and ozone, to increases in adipose tissue inflammation, as well as a plethora of other factors that are “tightly associated with obesity.”
It’s natural to believe that air pollution increases a person’s chances of becoming obese since it keeps people home, but it’s more complicated than that, according to Dr. Fatima Cody Stanford, an obesity medicine specialist and clinical researcher at Massachusetts General Hospital.
“Research suggests that air pollution may cause metabolic dysfunction — that is, it alters your metabolism and how your body accumulates cholesterol,” Stanford explains. “Air pollution also appears to be linked to the emergence of chronic disease, whether diabetes or obesity.”
However, “when there is air pollution, of course, it can impair normal physical activity, particularly in an outdoor setting,” she says.
According to Dr. Mark Conroy, an emergency medicine specialist at The Ohio State University Wexner Medical Center, the impact of air pollution on weight is connected with the advantages of exercise in general.
“Exercise has long been thought to have a strong link to enhanced health and body composition,” he explains. “Exercise can lower inflammation levels, enhance metabolism, and stimulate fat reduction in people who have high levels of inflammation.”
Stanford warns against blaming obesity solely on air pollution. “Obesity is a multifaceted, relapsing-remitting condition,” she explains. “Obesity can occur for a variety of reasons, and it is not contagious.
For some, air pollution may be one of the variables that contribute to some of the diseases that individuals suffer from, but for many, several factors are at work.” Among the factors are family history, medications, and persistent stress. “It’s critical that we don’t single out one element as being the cause of obesity,” she says.
Wang emphasizes that the study was carried out on a specific demographic — midlife women exposed to a specific range of air pollution (the median yearly PM2.5 concentration ranged from 12.3 g/m3 to 15.9 g/m3). As a result, concluding that the findings apply to everyone is impossible.
“However, our findings call for more research, particularly in high-exposure populations, to validate the link between air pollution and obesity,” he says. “This will help determine whether air pollution is a significant contribution to the obesity pandemic and lay the groundwork for future studies on intervention strategies.”