Today's obesity epidemic is also an epidemic of the health problems resulting from excess weight, such as diabetes, heart disease, and in some cases, early onset of puberty. The best way to combat obesity is to exercise more and eat less. However, we are learning that genetic factors may play a substantial role in obesity, and that something may be different about our genes now compared to forty years ago. New research is suggesting that genetic changes may be due to increased chemical exposure in the environment. This exposure is the most dangerous for babies still in the womb, but the effects may not appear until adulthood.

Hormones, Environmental Chemicals and Obesity
For any kind of developmental change to happen in the body, cells need signals, called hormones, to tell them what to do. Many of the chemicals from industry that are released into the environment resemble these hormones. These chemicals can be similar enough to hormones to provoke the same response that a natural hormone would. A grown adult has many mechanisms in their body to deal with such relatively small amounts of chemicals. However, small children, and especially babies in the womb, are at a much greater risk for dangerous effects from environmental chemicals because they have not yet developed these processes. When a child's body is still growing and developing, any disruption in normal levels of hormones can cause big changes.

New research published by Dr. Retha Newbold at the National Institute of Environmental Health Sciences is showing that certain environmental chemicals that interfere with hormone signals in the body while a child is developing in the womb can have serious consequences that may not be seen until adulthood.

Previous research has shown that chemicals called phytoestrogens are very similar to estrogen, and can react with our bodies much the same way estrogens do. These chemicals are present in plants such as soybeans, but they are also byproducts of many industrial processes and leak into our water and air supplies in tiny amounts. It has been suggested that babies who drink infant formula made from soy milk can be affected by these chemicals and start puberty much earlier than their peers. Dr. Newbold suspects that obesity could be a similar adverse effect to environmental chemicals that we do not see until children have grown into adults.

Some scientists do not think that our diet and exercise habits have changed enough in the last few decades to be the cause of our high levels of obesity. Previous research has shown that our current obesity epidemic coincides with an increase in industrial chemicals being released into the environment over the past 40 years. Other research has shown that the size of young mice can be affected by exposing them to different chemicals while they are still developing in the womb, and shortly after they are born. This shows that the chemicals we are inadvertently exposed to as developing babies could have substantial impacts on us much later in life.

DES: A Miscarriage Treatment Gone Wrong
One of the most well-known chemicals that affects developing babies much later in life is a chemical called diethylstilbestrol, or DES. DES is a synthetic estrogen that in the 1940s through 1970s was given to pregnant women to prevent miscarriages. However, it turned out to be harmful to developing babies, producing unintended effects such as rare cancers in adulthood.

Dr. Newbold has shown that if pregnant mice are treated with DES, we see similar cancers as we saw in humans. We also see that DES mice have fat deposits on different parts of their bodies and in different amounts than mice that were not exposed to the chemical. Scientists suspect that similar things are happening to humans who are exposed to various chemicals. These new chemicals are being called "obesogens", or factors that contribute to obesity. But they're not just getting into our bodies and making us fat. These chemicals are actually modifying our genes and changing which ones get used and which ones don't. They may turn off genes that we need to keep us skinny, or turn on genes that will make us store more fat but still feel hungry. We still don't know the full extent to which they affect us, but one thing seems likely - obesity may no longer just be about food and exercise.

Should We Still Exercise to Lose Weight?
Of course, diet and exercise are still crucial even if genetic conditions can predispose us to storing more fat in different ways, maintaining an active and healthy lifestyle is still just as important - and perhaps even more so if these genetic problems are an issue. The more we understand about how chemical exposures affect our genes, the more tools we'll have to keep future generations healthy.


Reference

Newbold, Retha, et al. (2008). Effects of endocrine disruptors on obesity. International Journal of Andrology. 31. 201-208.