For decades, public health discussion about metabolic dysfunction and weight regulation centered heavily on energy balance. Modern biomedical investigation now spans a complex interplay of endocrinology, toxicology, neurobiology, and neuropsychiatric research.

Researchers increasingly focus on a hidden class of environmental chemicals known as “obesogens,” a term coined by Felix Grün, PhD, and Bruce Blumberg, PhD, in their 2006 paper in the journal Endocrinology, “Environmental Obesogens: Organotins and Endocrine Disruption via Nuclear Receptor Signaling.” These endocrine-disrupting chemicals (EDCs), found in everyday plastics, food packaging, and consumer goods, actively interfere with how the human body processes weight, stores fat, and regulates metabolism.

Defining Obesogens and Their Mechanisms 

Grün and Blumberg minted the term “obesogens” to describe foreign chemical compounds that inappropriately alter lipid homeostasis and fat storage, change metabolic set-points, disrupt energy balance, and modify appetite regulation. Unlike standard nutritional inputs, these molecules act as hormonal impostors.

Exposomes, including obesogens, don’t replace the traditional “calories in, calories out” conversation, but they may help explain some nuances around weight regulation and fat storage, said Fady Hannah-Shmouni, MD, medical director of Eli Health and an endocrinologist, geneticist, and professor at the University of British Columbia in Vancouver, British Columbia, Canada.

“Some endocrine-disrupting chemicals can interact with receptors involved in how fat cells develop and store energy,” he said. “One of the best-studied examples is PPAR-gamma, a receptor that helps tell precursor cells to become fat cells. Certain chemicals, including tributyltin, have been shown experimentally to activate this pathway and promote adipogenesis.”

Luca Moretti, MD, an Italian specialist in hygiene and preventive medicine, said that substances like bisphenol A and certain phthalates can promote adipocyte differentiation, alter insulin sensitivity, and affect energy storage signals.

Moretti said that energy balance remains fundamental to body-weight management, but obesogens may modify an individual’s susceptibility to weight gain and metabolic dysfunction through several mechanisms, though human evidence strength varies and cannot attribute an individual case of obesity to a specific chemical exposure.

Expanding further on these pathways, Manish Arora, PhD, professor and vice chair in the Department of Environmental Medicine at the Icahn School of Medicine at Mount Sinai in New York City, and founder and CEO of LinusBio, said that EDCs affect lipid metabolism by encouraging fat cell proliferation and increasing fat accumulation.

“At the same time, there is evidence that EDCs interfere with how the endocrine system and the brain interact, producing a net increase in hunger,” he said. “More recent work has examined the impact of EDCs on the gut microbiome, where disruption to gut flora can lead to inflammation and impaired liver function, which in turn alters fat metabolism.”

While these compounds interfere with hormonal pathways involved in insulin sensitivity, lipid metabolism, and thyroid function, Hannah-Shmouni said to use caution when interpreting these findings.

“Much of what we know about the specific mechanisms comes from cell and animal studies, while human research has primarily found associations between exposure to some EDCs and obesity or metabolic outcomes. I’d think of these chemicals as one potential input into the system,” Hannah-Shmouni said. “Diet, physical activity, sleep, genetics, and underlying hormonal conditions still matter most, with overall energy balance being the most meaningful contributor.”

Ubiquitous Exposure: From Plastics to Pantries 

Modern life ensures continuous, low-dose exposure to chemical agents. Bisphenols, phthalates, per- and polyfluoroalkyl substances (PFAS), and various flame retardants permeate the modern material landscape.

When evaluating primary exposure sources, Hannah-Shmouni said that there isn’t a single source to label as the highest risk for everyone, as it depends heavily on the specific chemical. For bisphenols and certain phthalates, food is an important route of exposure because these chemicals can migrate from food-contact materials, including plastic packaging and can linings.

Moretti said that sources vary according to the chemical involved. He said that “bisphenol A and some phthalates have been used in plastics, packaging, and other materials that come into contact with food,” while certain phthalates and parabens appear in cosmetics and personal-care products. Moretti said that PFAS compounds are used in water-, grease-, and heat-resistant materials, with contaminated drinking water posing a risk in some areas, and that certain pesticides and persistent organic pollutants remain in the environment and food chain for years.

“For most people, exposure comes from a cumulative combination of products rather than a single source; phthalates and bisphenols migrate from plastic packaging, storage containers, and can linings into food,” Oparaji said.

Hannah-Shmouni said that the number and duration of exposure should be emphasized.

“These are repeated exposures from multiple sources over time. From a practical standpoint, food and food-contact materials are useful places to start because they are exposures people encounter regularly and have at least some ability to modify,” he said.

Arora said that there are many routes for these chemicals to get into the human body, but food is among the most prominent.

“Food is a major one, because so much of food processing and packaging involves plastics. It is almost impossible to buy food from a grocery store that has not been in contact with plastic at some point in its journey,” he said. “We also find micro- and nanoplastics in air and in waterways. Outside of occupational settings, food-related pathways and common household applications are the most significant sources.”

Clinical, Epidemiologic, and Public Health Perspectives 

The recognition of obesogens marks a shift in how the medical community approaches metabolic disorders, though debate persists regarding how clinicians should handle the evidence.

Hannah-Shmouni said that obesogen exposure does not need to become a routine obesity screen right now.

“We don’t have a validated clinical test that can tell a doctor that a particular patient’s obesity was caused by a specific environmental chemical, and I wouldn’t want this to distract from looking at the factors we can assess more directly,” he said.

Arora said that the main issue is that most clinical visits include almost no guidance on toxic environmental exposures.

“That needs to change,” said Arora. “An environmental screen should be part of every wellness check, as routine as measuring blood pressure. Detailed guidance on how to reduce exposure is essential. Prevention is going to be far more relevant here than developing costly detox-type therapies.”

“Clinicians should consider chemical exposure as a plausible contributor within the broader biology of obesity without serving as a replacement for evaluating nutrition, physical activity, or sleep, [and] discussions should not become another source of patient blame,” said Nneoma Oparaji, MD, an obesity, lifestyle, and internal medicine specialist.

Recent epidemiologic literature introduces important nuances regarding causality. A 2025 review published in the journal Ecotoxicology and Environmental Safety examined 75 human epidemiologic studies and found relatively consistent associations for some phthalates and bisphenols, particularly in children and women, while results for PFAS were substantially more heterogeneous.

This may also highlight a critical reverse-causality problem: Individuals consuming more packaged or ultraprocessed foods may simultaneously experience higher caloric intake and higher food-contact chemical exposure.

From a public health perspective, the focus should be further upstream, said Moretti, utilizing regulation of food-contact materials and water quality monitoring to reduce population-wide exposure.

Arora is founder and CEO of LinusBio, which develops and sells environmental exposure testing. Hannah-Shmouni declared being the founder and managing partner of FHS Capital, an investment and advisory firm focused on health, biotechnology, and AI-driven longevity ventures, and serving as medical director at Eli Health. Moretti and Oparaji reported having no disclosures.