July 8, 2011

Can plastic make us fat?

photo: flickr.com | u-o-0024

~ from Environmental Health News

The rates of obesity and overweight in adults and especially in children are on the rise, though some recent studies indicate that the rates may be at least leveling off among adults. According to the Centers for Disease Control, 34 percent of adults are obese and a further 34 percent are overweight. Twenty percent of children 6-11 years old are also obese, as are 10 percent of children 2-5 years old.

Prenatal exposure to low levels of BPA caused rats to become obese and unhealthy as adults, finds a new study. Pups exposed to a low dose through their mothers while in the womb and nursing – but fed a balanced diet as they grew – were fatter and had a suite of metabolic problems later in life when compared to unexposed rats.

Worse health effects occurred at a younger age in exposed animals fed a high fat diet. The effects were seen at a low dose currently considered safe by the U.S. Environmental Protection Agency but not at a medium or high dose.

Studies find almost everyone in the United States is exposed to BPA since it is used widely in polycarbonate plastics, dental sealants, resins that line food cans and some store receipt paper.

What does it mean?

Exposure to a low dose of bisphenol A (BPA) while in the womb and while nursing may increase the risk of obesity and a suite of metabolic problems even if eating a balanced diet into adulthood, finds a study with rats. Similar effects were seen earlier in animals exposed to the same low dose but fed a high-fat diet. These health effects were not seen in the growing rats exposed to medium and high doses.

This study is one of a number of recent studies that suggest that BPA may have adverse health effects at or even below the current reference dose. It also adds more detail to studies that point to BPA affecting weight and metabolism.

Even though this was an animal study and the results can’t be directly applied to people, it’s a first step in understanding how environmental chemicals like BPA may influence development in ways that last a lifetime. More research is needed to determine if the results apply to people.

The research shows one example of a chemical for which the health effects observed after a small dose are not just a milder version of the health effects that observed after a big dose. Rather, the health effects seem to be completely different at the different dose levels.

This study finds that exposure to BPA while in the womb and from the mother’s milk increases weight gain and a host of health problems associated with obesity later in life. The effects of BPA were magnified in rats that were fed a high fat diet after weaning. BPA exposure at the early stages of development may lead to a “metabolic reprogramming” that sets the exposed offspring on an early path toward an increased risk of obesity and its associated health complications.

Additionally, this research suggests that we may need to rethink the method for testing the toxicity of certain chemicals by evaluating the potentially toxic effects of chemicals at doses that reflect realistic human exposures. Health effects were only observed at the lowest dose in this study – a dose that is supposed to reflect a “safe” exposure to BPA.

photo: flickr.com | AndrewRichardMills

The risk of obesity is clearly influenced by the increasingly high-fat and calorie-dense diets of most of the world’s population. In addressing the obesity epidemic, less attention has been paid to the potential role of other environmental exposures.

Because the time before and after birth is an especially crucial period for development, changes in the early life environment can have potentially profound impacts later in life. This study showed that the time period surrounding birth may be particularly crucial for the effects of BPA exposure on later metabolism. Researchers are now working to understand whether these sorts of early life exposures in humans may be contributing to the obesity epidemic, especially among children.

Read the entire synopsis at EnvironmentalHealthNews.com.

Just one word: Plastics.

what is bpa?

Bisphenol A (BPA) is a component of polycarbonate plastics used for food and drink containers. It is also found in resins that line food and beverage cans, thermal paper used to print many retail receipts and dental sealants.

Humans are exposed to BPA through eating, drinking and absorbing through the skin. Eating canned foods and handling retail receipts may increase exposure. Because the chemical is so common, exposure is widespread. Researchers detect BPA in over 90 percent of urine samples tested in the United States. BPA can cross the placenta into the womb during pregnancy and can pass from mother to baby after birth through breast milk.

BPA is an endocrine disrupting chemical, or EDC. These chemicals can interfere with the natural signals of the endocrine system, which uses hormones to relay important biological messages throughout the body. Evidence is increasing that BPA exposure may increase risk of obesity and its complications. Previous studies in animals show that BPA exposure early in life increases body fat and weight gain later in in life. Some studies in humans have shown that exposure to BPA and other endocrine disrupting chemicals is associated with increased risk of obesity, cardiovascular disease and metabolic syndrome.

Metabolic syndrome is a set of medical problems associated with obesity, including increased insulin resistance and blood insulin levels (hyperinsulinemia), increased glucose tolerance and blood sugar levels (hyperglycemia), high blood pressure (hypertension), and high levels of triglycerides and LDL (“bad cholesterol”) in the blood. Individuals with metabolic syndrome are more likely to develop Type II diabetes and cardiovascular disease.

Insulin is a hormone that regulates metabolism in the body. Normally, when blood sugar starts to rise after eating a meal, insulin rises as well so that muscle and fat cells will take up the sugar, keeping the balance of blood sugar level. As people become overweight and obese, their cells often stop responding to the normal levels of insulin, leading to insulin resistance and potentially dangerous elevated blood sugar levels.

*** Originally posted on my I Count for myEARTH blog via EnvironmentalHealthNews.com.

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