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Obesogens: Chemicals that cause weight gain

It's not all diet and exercise.

Obesity is an increasingly common disease in the United States. The most recent statistics gathered from 2017 to 2020 identify 41.9% of Americans as obese, with the prevalence of severe obesity nearly doubling to 9.2% over the last two decades.

Obesity is a serious condition, increasing the likelihood of health problems like heart disease, stroke and type 2 diabetes — some of the leading causes of premature death.

We’ve all heard the standard solutions: eat less, exercise more. But there’s more to it: chemicals in our daily lives make it easier to unintentionally gain weight and may even make it more difficult to lose it.

These insidious chemicals are called “obesogens” and some doctors are incorporating this research into their practices and recommendations.

What are obesogens?

Obesogens are a type of endocrine-disrupting chemical.

Quick reminder: your endocrine system is made up of glands that make hormones. To put it simply, those hormones serve as your body’s “chemical messengers” that control many important parts and functions of the body.

Obesogens, as endocrine-disrupting chemicals, hijack that messenger system and can wreak havoc on your health in a variety of ways.

Obesogens are generally defined as chemicals that can cause the human (and animal) body to produce more fat than it normally would. Obesogens can include substances we often think of as fattening, like sugars, but also include an array of chemicals used in all sorts of products, such as BPA, phthalates and more.

How do obesogens work?

Obesogens work in many ways. The way they impact your body depends on the type of obesogen, and can include:

  • Disrupting your metabolism, causing your body to produce new or larger fat cells
  • Blocking fat cells from releasing stored fat to use as energy
  • Altering your eating habits
  • Impacting your gastrointestinal tract, which affects how food is digested.

Exposure to obesogens can occur as early as prenatal development. Obesogens can act across one’s lifespan - but prenatal exposures are most sensitive to their effects and can cause obesity later in life.

Where am I being exposed to obesogens?

food container chemicals

Ditch the plastic food storage containers: they leach toxic chemicals into your food.

Credit: jmalov - Getty Images Signature

Unfortunately, all over the place.

Many everyday products contain obesogens, including:

  • Plastic food storage containers
  • Plastic toys
  • Nonstick cookware
  • Personal care products
  • Cleaning supplies
  • Medical devices
  • Flame retardants
  • Pesticides
  • Processed food additives: preservatives, emulsifiers, flavor enhancers, high fructose corn syrup
  • And more

Chemicals that are obesogens are added to products such as these because they serve a purpose — various obesogens can make plastics harder or more flexible, make textiles stain or water resistant, packaging grease resistant, etc.

Scientists, researchers and doctors are now pushing for those chemicals to be removed as unintentional health impacts are being discovered.

What are the most common obesogens?

Phthalates are an obesogen often added to items such as plastic children's toys.

Credit: Capuski - Getty Images Signature

  • Many pesticides: for example, DDT. Though it was banned in the U.S. in 1972 due to environmental impacts, DDT persists for a long time in the environment and in animal tissues and can cause health effects generations after exposure
  • Air pollution: studies have shown that early exposure to air pollution increases the risk of childhood obesity
  • Phthalates: often added to plastics to increase their flexibility and found in cosmetic products, hair and skin care products, feminine care products, fast food wrappers, sunscreens, children’s toys, food storage containers and more
  • Bisphenol-A (BPA): while it may be more common to find BPA-free products these days, BPA is only officially banned in baby bottles. You may still find BPA in water bottles, canned food linings, receipts, food containers, toys and more. Keep in mind, too: just because a plastic product is BPA-free does not mean the alternative chemical used in the product is any safer
  • PFAS: called “forever chemicals” for their inability to break down in our bodies and in the environment, PFAS chemicals are found in a vast number of consumer products. Read our full guide on PFAS here — and check out our investigation into PFAS in consumer products here.

How can I avoid exposure to obesogens?

food contact chemicals

Cookware such as cast iron is a safer alternative to nonstick.

Credit: Anshu A/Unsplash

Avoiding obesogens is difficult. However, any step to limit your exposure can make a difference. Here are some ideas:

  • Avoid storing or purchasing food in plastic. Especially avoid heating foods in plastic — this includes frozen dinners and vegetable steamer bags! Heating plastic makes it much more likely that chemicals like obesogens will leak into food
  • Use glass or stainless steel containers and bottles instead of plastic
  • Use cast iron, stainless steel or enameled cookware. Nonstick coatings are known to contain toxic chemicals like obesogens
  • Check your personal care products against databases like the EWG’s Skindeep Cosmetics database or the Clearya mobile app. A general rule of thumb for your personal products: look for organic ingredients, and “less is more” - the fewer ingredients, the better
  • Opt for fragrance-free products unless the fragrances are explicitly disclosed and safe
  • Filter your water! There are a number of options (for a variety of budgets): filter pitchers you can keep in your fridge, under-sink filters and more
  • Skip the flame-resistant and water-repellent carpets, furniture, tablecloths, etc. — the chemicals that make those properties possible are usually obesogens.

Learn more about obesogens and your health

Check out some of our other reporting on obesogens:

Chemicals in everyday products are spurring obesity, warns a new review

Doctors advocate for treating obesity as an environmental problem

Op-Ed: The medical community is missing a major piece of the obesity puzzle

Subscribe to our Above the Fold newsletter to send important news about the environment and your health to your inbox.

Want to get into the nitty-gritty science? Check out EHS program HEEDS - Healthy Environment and Endocrine Disruptor Strategies - for a more technical exploration of obesogens research. For example, check out their comprehensive review articles on obesogens coauthored by dozens of experts in the field.


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