Unexplained Weight Gain: Obesogens

Unexplained weight gain can be triggered by obesogens. In the past decade, the internet has been flooding with topics regarding different easy steps on how to reduce those extra pounds. Most suggestions are diet regimens, exercise programs, medications, and even strap-on-fat-busting machines. With the numerous links to possible solutions for weight-reduction, it is evident that most people want to lose weight and be healthy and do not like being overweight or obese. It becomes frustrating when you are apparently doing everything right, but the scale still doesn’t budge.

Conventional wisdom would mostly blame sedentary lifestyles, age, overeating and processed food for the rise in obesity. However, recent studies have shown “obesogens ” to be a contributing factor weight gain and obesity.


Mortality rates increase with increasing degrees of weight gain, as measured by body mass index (BMI). The goal is to maintain BMI between 18.5-24.9 kg/m2. There is an increased risk for co-morbidities when overweight (BMI between 25-29.9 kg/m2) and obese (BMI of 30 kg/m2 or greater). Disorders such as type 2 diabetes, hypertension, and cardiovascular diseases can develop in these individuals with poorly controlled weight gain.

Around the globe, 2.8 million people die each year, and an estimated 35.8 million (2.3%) of the global disease burden are caused by being overweight and obese. According to the WHO, the prevalence of overweight and obesity were highest in the regions of the Americas with the United States having (26% obesity, with a total of 62% overweight) and lowest in Southeast Asia (14% overweight in both sexes and 3% for obesity).


In 2006, Bruce Blumberg, a biology professor at the University of California coined the term “obesogens” after discovering that tin-based compounds predisposed laboratory mice to gain weight. These chemicals alter fat metabolism that eventually leads to obesity.

So how exactly do obesogens affect our bodies? In a mini review by Felix Grün and Bruce Blumberg (2009), there are at least four possible mechanisms through which obesogens make you gain weight:

1. Obesogens have estrogenic effects.

Studies in adults taking estrogen hormone replacement show that estrogen has antiobesogenic potential. However, fetal or neonatal exposure can lead to obesity later in life.

Another study identified a gender-related adipogenic effect in juvenile mice. The differences in the outcome from estrogen exposure probably reflect the ability of obesogens to activate the estrogen receptors that can lead to weight gain or obesity.

Female mice exposed to diethylstilbestrol (DES) initially led to depressed body weight which was followed by weight-gain upon reaching adulthood.

Male mice on the other hand that was exposed to DES displayed a dose-dependent decrease in overall body weight.

2. Obesogens cause you to produce and store more fat.

This mechanism points out that obesogens may stimulate certain receptors that are responsible for increasing the number and volume of your fat cells. The activation of the said receptors allows differentiation of fat cell progenitors and regulates lipid biosynthesis and storage.

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3. Obesogens make you feel hungrier

Some drugs are noted to have an effect in the hypothalamic-pituitary-adrenal (HPA) axis. This axis plays an imperative role in the regulation of appetite and satiety. The stimulation of this axis includes a variety of signals from different parts of the body such as those from the digestive tract, fat tissue, and brain. These signals could be potential targets of obesogens.

Indeed, disruptions in regulation of body weight, due to increased desire to eat, could be observed in various neurological disorders and may be a result of medications intended for their treatment.

4. Obesogens make you burn less fat.

Fat cells do not increase after puberty. Although the axis mentioned above could be a plausible cause for obesity, much of the control over the capacity for adaptation to metabolism resides in the hypothalamic-pituitary-thyroid (HPT) axis.

Thyroid hormones activate several metabolic components that promote energy consumption and decreases fat accumulation.The decrease in thyroid hormones causes a propensity for metabolic syndrome and obesity.

In addition to thyroid hormones, glucocorticoid hormone levels play a critical role in the HPA axis. Increased glucocorticoid production contributes to the production of mature white fat cells, hence leading to obesity. Thyroid hormones regulate fat metabolism through adipocyte differentiation. Adipocyte “white” fat cells store fat for energy and metabolism. Researchers have always thought that most of the fat cells are produced immediately after birth, and the numbers stay consistent into adulthood. When adults gain and lose weight the number of fat cells in the body stay the same. This fact is interesting because just like every other cell in the body, fat cells are constantly dying off and being replaced. When comparing the composition of fat cells between a lean body and obese body, there weren’t necessary more fat cells, the fat cells were just larger. If the subject was obese during childhood then, the fat cells count was typically greater.


According to Jerry Heindel, who leads the research program in obesity at the National Institute of Environmental Health Sciences (NIEHS), there are about 15-20 chemicals identified to be potential obesogens. Majority of these chemicals causes weight gain from developmental exposure.

Obesogens are sneaky chemicals that can be found in things we usually use on a daily basis. You’d be surprised to find out that they are closer to you than you think. Here are some of their most common sources:

1. Containers: BPA exposure

Bisphenol A (BPA) is a chemical used in manufacturing plastics marked with the recycle symbol ‘7’ or with the letters ‘PC’ near the recycle symbol. These could be found in plastic bottles or containers, linings of canned products, receipts, and some devices. Because of its structure, it can mimic estrogen and can cause similar effects in the body, hence acting as a xenoestrogen. Although BPA causes reduction of fat cells, it stimulates more fat production, hence leading to weight gain.

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In addition to weight gain, evidence-based findings noted that BPA can cause several co-morbidities such as cardiovascular diseases, type 2 diabetes, neurologic disorders, pre-cancerous lesions in the prostate and mammary glands, and early onset of puberty in girls. However, authorities have not totally ruled this in as a definite threat to human health due to several conflicting studies and inadequate data.

Currently, BPA use has been banned in baby bottles and products by the Food and Drug Association. They are still conducting researches and reviews on the definite effects of BPA in humans and supports finding alternatives to BPA as a chemical additive.

2. Chemical pesticides: Atrazine exposure

Atrazine has been touted to be of great benefit to crop growers; however, there are limited studies to backup that claim. Over a decade ago, the chemical was banned in Europe due to contamination of the groundwater that eventually found its way into the tap water system. However, it is still widely used in the United States as an herbicide.

Some pesticides and fungicides, including atrazine, are known xenoestrogens. These chemicals are also being blamed for the severe death of bees.

They disrupt thyroid hormone balance, increase fat production and decreases fat burning processes.Atrazine has been linked to increasing BMI in children and can cause insulin resistance in mice, both leading to obesity.

However, similar to BPA, atrazine is yet to be proven as a definite cause of obesity, especially in humans.

3. Smoking

It has been noted that maternal smoking during pregnancy causes low-birth weight and length. However, before one year of age, children of smoking mothers display catch-up growth with increasing weight gain in the succeeding years. Studies suggest that smoking during the first trimester has a bigger impact on that child becoming overweight.

Mechanisms of this factor are thought to be due to insulin, leptin, and glucocorticoid resistance, all of which lead to increased fat production and storage with decreased fat metabolism.

Overall, while the weight gain in children due to this factor is small, its effects are consistent and persistent, hence indicating a risk for obesity by maternal smoking. This contributes to the overall increase in weight gain around the world.

4. Non-stick pans and microwaveable food items: Perfluorooctanoic acid (PFOA) and Teflon

Exposure to this chemical during pregnancy eventually leads to its expression in breastmilk that is consumed by the infant. According to studies, it was noted that upon reaching adulthood, these infants gained more weight as compared to those who had lesser exposure to PFOA.

These babies had elevated levels of leptin, a hormone secreted by the fat cells. This hormone supposedly suppresses your hunger, however in obese children with elevated leptin, and researchers believe that the brain can become resistant to its effects.

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5. Soft plastics and scented items: Phthalates

Phthalates are synthetic estrogen that act as endocrine disruptors. Phthalates are found in thousands of products such as toys, beauty products, candles, air fresheners with synthetic scents, pharmaceuticals, shower curtains and paint. They can seep out to contaminate food, air, and water sources. Exposure to these chemicals allows absorption through the skin, the oral route, or respiratory tract.

Phthalates cause increased susceptibility to weight gain by affecting receptors called PPARs involved in the metabolism. Studies have shown links with abdominal obesity, increased waist circumference and insulin resistance, that are more notable in males 20-59 years old. Exposure during pregnancy predisposes infants to genital malformations, undescended testes and low-testosterone levels.


Obesogens are technically in almost everything and are everywhere. It is virtually impossible to avoid them! However, don’t fret. There are a few things you can do to reduce your exposure to these chemicals and minimize possible complications in the long-run.


  • Encourage your household to eat organic products rather than those with pesticides and chemical fertilizers.
  • Reduce the use of plastic containers or products.
  • Find alternatives containers such as glass, ceramic, BPA-free products, and the like.
  • Use essential oils for aromatherapy in your house, try to avoid air fresheners and candles.


These are just measures that reduce your exposure to sources of obesogens. It is important to take note that most obesogens are not proven to cause harmful effects to humans. However, there is nothing with preventive measures. Remember, a little proactiveness goes a long way. Trust me, your body will thank you in the future.


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Unexplained Weight Gain: Obesogens