Worldwide obesity has more than doubled since 1980 and if current trends continue, one in five people will have obesity by 2025. In the United States, over 35 percent of adults and nearly 17 percent of children have obesity.
Lifestyle factors such as diet and activity levels have long been considered leading contributors to developing obesity. Adding to this problem is an increasing amount of scientific evidence suggesting that endocrine disrupting chemicals (EDCs) may also play a role. Two terms have been coined in describing the role of certain chemicals in metabolism and obesity.
When somebody says they have a “good” or “slow” metabolism, they’re talking about their endocrine system and the hormones they produce. When your body needs nutrition, hormones spur the metabolic responses—like hunger—that prompt you to seek food.
When EDCs block connections between hormones and their receptors, they “reprogram” the parts of the endocrine system that govern metabolism, energy balance and appetite. EDCs change the sensitivity to glucose (sugar) and the metabolism of lipids (fatty acids). All of this predisposes a person to gain weight.
EDC-related weight gain involves more than just adding a few pounds. EDCs can alter the way our bodies consume food and store energy; even effecting individuals across generations.
To understand, it's important to know that metabolism functions on the cellular level. For instance, hormones produced by the thyroid gland regulate day to day metabolism of the body’s cells. EDCs found in plastics, fragrances, industrial waste, and pesticides can disrupt the thyroid’s normal processes, and therefore, can disrupt day to day metabolism.
Studies have shown that certain EDCs interfere with the body’s control of appetite and increase energy storage in fat tissue such as the chemical BPA found in many consumer products from aluminum cans to water bottles. Evidence also indicates that BPA exposure in the womb can lead to obesity later in life.
Weight gain is only one effect of EDCs. In rodent studies, mothers exposed to a chemical in one of the most commonly used fire retardants in the United States led to altered levels of thyroid hormone secretion. After giving birth, their pups grew up to develop not only obesity but also heart disease, early puberty, and insulin resistance.
The hormone insulin is necessary to regulate blood sugar levels and prevent diabetes. Certain EDCs impede these functions, increasing the enzymes that make glucose while reducing the ability of the pancreas to secrete insulin in response.
In recent studies, mice exposed to the chemical DDT became insulin resistant, which can ultimately lead to diabetes. In a striking note, nations where DDT is still in use such as South Africa and India have seen dramatic increases in diabetes, which may be due in part to environmental exposures.
Although DDT has been banned in many nations, other EDCs related to metabolic syndrome (a group of factors that raise the risk of heart disease, diabetes and stroke) are still widely used. In Denmark, children exposed to PFCs—industrial chemicals found in a variety of consumer products—were more likely to show early signs of metabolic syndrome.
Because many factors contribute to obesity and related conditions in people, more research needs to be done to establish causality. That said, numerous studies have linked BPA exposure with cardiovascular disease and hypertension, and recent evidence in animals suggests that BPA may trigger irregular heartbeats.
Knowing the effects of EDCs is an important first step. Here are a few resources to learn more: