Do Chemicals in Our Environment Cause Weight Gain?

Keris KrennHrubec, Carly West, and Diana Zuckerman, PhD, National Center for Health Research

Today’s obesity epidemic has also resulted in an epidemic of diabetes, heart disease, some types of cancer, and early onset of puberty. Obesity is caused and influenced by many factors, but this article will help explore how some chemicals cause obesity.

Hormones, Environmental Chemicals and Obesity

Hormones are involved in almost every process in the human body, including where and how much fat the body stores. Hormones help to control how many calories to burn right away and how many to store as fat. Chemicals that influence our hormones and can lead to obesity are called “obesogens.” These chemicals get into our bodies through food, water, and products that we use.

Many of these chemicals “look” like hormones to our bodies. The body reacts to them like they do to a hormone. Other chemicals interfere with hormones, such as sex hormones like estrogen and testosterone. These chemicals are called “endocrine disruptors” because they change the way our hormones operate. Chemicals can cause the body to “think” that it has to store more fat than it needs, or they can interfere with how our bodies use fat. Babies in the womb are especially vulnerable to obesogens.[1] Exposure to these chemicals increases the chance that they will become obese as a child or adult.[1] This article will describe several of these endocrine disrupting chemicals.

Per- and Polyfluoroalkyl Substances (PFAs)

PFAs are in many common household products, such as herbicides, pesticides, plastics, and detergents.[2] PFAs also create the non-stick surface on cookware, protect carpets and clothes against stains, and create a foam that helps control fires.[3]

Most people are regularly exposed to PFAs. Although research is needed to better understand PFAs, they are known to increase the risk of obesity and osteoporosis. One study found that PFAs may lower testosterone and increase inflammation.[4] In addition, pregnant women with higher levels of PFAs gained more weight during pregnancy than those with lowers levels of PFAs.[4]

Bisphenol A (BPA)

BPA affects hormone levels because it is synthetic estrogen (“the primary female sex hormone”).[5] BPA exposure can be harmful from birth through adulthood, causing reproductive, developmental, and behavioral changes.[6]  In addition, BPA exposure can increase the risk of developing obesity, diabetes, and cardiovascular diseases.[7]

BPA was commonly used in hard plastic containers for sports water bottles and food containers, and also to line food cans. After consumers protested, BPA was taken out of many baby bottles and other beverage containers, but the replacements had unknown risks, some of which scientists have been found to be similar to BPA. To avoid BPA exposure, it is recommended to avoid plastics (such as food containers), to not put plastic in the microwave or dishwasher, and to use glass containers for food and drinks when possible.[5]


Phthalates, unlike BPA, do not act like estrogen, but rather block androgens (hormones like testosterone in both males and females). What BPA and phthalates have in common is that they appear to contribute to a similar imbalance of sex hormones.

Phthalates soften plastic to make it flexible and durable, so these chemicals are added to materials such as vinyl flooring and food containers.[8] These chemicals are also found in fragrances for many household and personal care products, such as lotions, nail polish, skin creams, shampoo, and air fresheners.[8] Although a 2008 federal law prevents the riskiest phthalates from being used in toys and plastics, people of all ages are still regularly exposed to products with phthalates.[8] People are exposed to phthalates through food, drink, the air we breathe, and the products we put on our skin.[8] Babies in the womb can also be exposed because phthalates can travel through the placenta.[9]

Research indicates that phthalates increase a person’s risk of becoming overweight or obese.[9] Obesity increases the risk of developing diabetes. One study found that children recently diagnosed with diabetes had more phthalates in their bodies than children who do not have diabetes.[10]

Tributyltin (TBT)

Tributyltin (TBT) is a chemical used to kill fungi, to preserve wood, and to prevent water creatures from sticking to boats.[10] When humans are exposed to this fungicide, it can disrupt hormones by blocking testosterone from being converted into estrogen. [1] Higher levels of testosterone have been linked to obesity.[12]

How Do These Chemicals Potentially Cause Obesity?

At very high doses, many of these chemicals cause a person’s body to burn fat rather than store fat.[1] This is similar to the effect of extreme dieting. Extreme dieting can result in a body conserving calories to prevent starvation, and thereby storing extra fat.

People whose metabolisms have developed in this way may also be less sensitive to insulin, which is a hormone secreted by the pancreas. Insulin moves sugar from our bloodstream into our cells so that we can use it for energy. People who are less sensitive to insulin may develop chronically high blood sugar levels. When these levels become very high, people may develop type 2 diabetes.

The chemicals may also cause babies in the womb to make more fat cells. This means that they can store more fat and are more likely to become obese.

Is This Why I Can’t Lose Weight?

If you are like many people who struggle with weight loss, you may eat the number of calories you are told that you need, but still feel hungry. Or, you may eat the same number of calories as thinner people but still gain weight when others stay thin. When you exercise, you may not see results as quickly as expected.

After reading this article, you may wonder if exposure to hormone-disrupting chemicals can make it more difficult to lose weight. There are no clinical trials to determine whether exposure to chemicals in infancy or later in life contributes to weight control problems because it would be unethical to intentionally expose someone to these chemicals. So, the studies of humans are based on real world evidence – people with higher exposures are more likely to be overweight. In the real world, epidemiological studies, it is hard to measure and statistically control the many factors that might affect weight. However, as shown in this article, there is growing evidence to suggest that reducing exposures to endocrine-disrupting chemicals could help to prevent obesity as well as other health problems.


All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.

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  3. PFAS research. Updated May 19, 2020.
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