Doctors are beginning to incorporate obesogen science into their treatment of patients, but face barriers to making the practice widespread.
When Dr. Rob Sargis sees a patient struggling with obesity, his recommendations go beyond diet and exercise. He may advise them to stop heating things in plastics, or to avoid congested roads during rush hour.
Sargis, a practicing doctor and professor of medicine at the University of Illinois, is one of a number of doctors incorporating the science of obesogens — endocrine-disrupting chemicals that spur obesity — into their clinical practice.
Obesogens are a subset of endocrine-disrupting chemicals — man-made compounds that alter hormone activity. They are generally defined as any chemical that can cause the human body to produce more fat than it normally would, and can include substances we usually think of as fattening, like sugars or artificial sweeteners.
However, obesogens are not only found in food, rather entering the body through other consumer products, like makeup, shampoos, soaps, plastics, and food packaging. People are exposed through contact with the chemicals and through ingestion of contaminated foods. The chemicals are also shed from such products and can accumulate in household dust, which people breathe in. PFAS, or per- and polyfluoroalkyl substances (toxic chemicals used in many consumer and industrial products) are another example of obesogens, as is bisphenol- A (BPA).
By disrupting hormone activity, these chemicals can spur obesity in a number of ways. They can alter metabolism, cause the body to produce new fat cells, alter eating behavior, and even change the way food is digested.
To Sargis, incorporating an understanding of obesogens into clinical practice is part of the goal of medicine as a whole: to build a healthier society. Obesogenic chemicals have other harmful health impacts too — for example, PFAS and BPA are also linked to certain cancers and reproductive problems. Reducing obesogen exposure is beneficial across the health spectrum.
“What we’ve seen in medicine over the last few years is this shift from individual factors, like genetics, lifestyle and diet, to an embracing of the social determinants of health, including things like food, environment, exercise and education,” Sargis told EHN.
However, Sargis and other doctors interested in using the obesogen framework face barriers, such as difficulties gathering data on obesogens, a bias toward focusing on diet and exercise, and inadequate medical school training in environmental exposures.
In addition, a lack of regulation of obesogens makes it hard to reduce the exposures — even for patients who are aware of the risks. “The challenge is that there are systemic forces that you have to fight, and a lot of that's policy, and a lot of that policy is embedded in politics,” Sargis said.
Lack of data
Doctors are hesitant of incorporating obesogens in their clinical practice as there's no data showing that if a person reduces their obesogen exposure, they can lose more weight.
A major obstacle to incorporating an understanding of obesogens into clinical practice is that doctors are sometimes not convinced by the data available. While plenty of data exists to show a correlation between obesogen exposure and obesity, there is less data that shows that if a person reduces their obesogen exposure, they can lose more weight.
Gathering that data is difficult, but possible, said Sargis. However, the ubiquity of obesogens in everyday products, as well as the lack of transparency from companies about the chemicals in their products, makes designing such a study difficult. The sheer number of chemicals that would need to be tested — there are more than 9,000 types of PFAS, for example — also adds to the challenge.
Jerry Heindel, a biochemist and founder and director of HEEDS*, a coalition of researchers advocating for better regulation of chemicals, told EHN that doctors and patients could benefit from an accessible and cheap way to measure exposure to obesogens. That way, patients could hypothetically see if their exposure levels drop over time as they worked to eliminate obesogens from their daily life. For now, he said, patients would need to pay for the tests themselves, but he hopes insurances would cover the tests in the future.
Jenna Hua, a doctor-turned-CEO of medical testing company Million Marker, thinks her company’s product could play a role. Million Marker offers at-home test kits that measure the levels of 13 common endocrine-disruptors, some of which also act as obesogens, in a person’s urine. The tests are able to detect BPA, two BPA alternatives, five types of phthalates, four types of parabens, and oxybenzone. It’s “quite empowering,” Hua told EHN, when someone using the tests can see their exposure levels drop as they swap out products they’re using that include obesogens.
The type of testing that Million Marker offers would be another tool in managing weight loss. “It would not be possible to tease out what part of weight gain is due to obesogens,” Heindel said. “The doctor would have to explain to the patient all the possibilities and how to address each of them to reduce their weight.”
As more patients recognize that obesogen exposure is a threat to their health, Hua said, the public may be more inclined to pressure governments to regulate endocrine-disrupting chemicals. Most obesogens are not currently regulated in the U.S., for example, the Food and Drug Administration does not restrict the use of BPA in food packaging, and there are no federal standards limiting PFAS discharges in drinking water.
Bias toward individual factors
One of the reasons that obesogens have been overlooked, Sargis said, is that treatment of obesity is biased toward individual factors like diet and exercise. “There’s an inherent bias that this is somehow a personal failing,” he said.
That kind of thinking, he said, might be rooted in conventional beauty standards and the idea that obesity is an aesthetic problem more than a health problem. Research has shown that in the U.S., obese individuals are often highly stigmatized and labeled as lazy, unmotivated, and lacking in self discipline. Medical students themselves can perpetuate these stigmas — one study of third-year medical students at Wake Forest University found that more than one-third of the future doctors associated obesity with negative attributes, with the majority of students, 72%, reporting that they preferred “thin” people to “fat” people.
Enhancing education, growing awareness
A lack of training in environmental exposures in medical schools is a major obstacle.
There is still a huge gap in medical school training when it comes to obesogens, Sargis said. The sheer volume of knowledge medical students are required to learn leaves little room for discussions about environmental exposures. The end result is that doctors often leave environmental exposures out of their practice — for example, a 2015 study of maternal and child physicians found that environmental health assessments were “infrequently” part of routine counseling of patients.
Dr. Jamaji Nwanaji-Enwerem, a 2021 graduate of Harvard Medical School and current resident at the Emory University School of Medicine, said he got very little training in environmental exposures in medical school. “Medical students across the nation are not being extensively exposed or trained formally on the effects of the environment on a patient's health,” he said. Rather, Nwanaji-Enwerem, who is also an assistant professor of environmental health at Emory, gained his expertise in learned about environmental exposures through classes outside of the medical school and through his own practice.
One patient suffering from hypertension and respiratory problems inspired Nwanaji-Enwerem to write a paper about the importance of considering environmental risks. In the paper, Nwanaji-Enwerem writes that other doctors should ask their patients about the chemicals they come into contact with at work, and whether they wear proper personal protective equipment to protect them from chemical exposures.
To supplement medical school training about obesogens, Heindel said, professional societies, like the Endocrine Society, Obesity Society and Pediatric Society, could be a good starting point to help young doctors learn about obesogens. For example, East Carolina University professor and pediatrician David Collier first learned about environmental exposures at a conference for academic practicing pediatricians. According to Collier, there need to be “many touch points” where researchers and doctors can have such conversations.
Additionally, Sargis said, doctors get very little time with patients. It’s difficult to squeeze in a conversation about the risks obesogens pose during a 20-minute consultation. To help, he said he’d like to see more educational materials available to patients after their visit, such as short videos explaining obesogen exposure.
Part of the solution, too, could be getting doctors to care more about the environmental health of the neighborhoods where their patients live, Sargis said. While doctors might not want to engage in political discussions, they might play a key role in decreasing the chemical exposure of their patients. Getting doctors involved in discussions about housing, city planning, building codes, policing, water use, and environmental policy could make a difference for the health of people living in those communities, he said.
“When you have physicians that aren’t willing to step out of the clinic and into these discussions, it becomes difficult,” he said. “We really need physicians, scientists, and health policy experts at the table.”
*HEEDS is a program of Environmental Health Sciences, which publishes EHN.org.
*Editor's note: An earlier version of this article quoted Bruce Blumberg, professor of Developmental and Cell Biology, and Pharmaceutical Sciences at the University of California Irvine, asserting there is no evidence that lowering obesogen exposure reduces weight. Blumberg has published multiple scientific papers and a book, The Obesogen Effect, consistent with the role of obesogens in controlling weight.
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