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Disrupting Nature

The genetics of weight

We all know exercise and diet can make a big difference in our weight and overall health. But some of us assume that if overweight people exercised more and quit eating calorie-laden fast foods, they would slim down. Well, it's not that simple. We now know that these assumptions are wrong. A recent article by Gina Kolata in The New York Times reported that research physician Jules Hirsch studied eight patients who had been fat their whole lives. Hirsch put them on a 600-calorie liquid diet, and the patients each lost approximately 100 pounds. The doctor continued to study the patients and found that "they all regained."    

In repeating the research, Hirsch and others found that while the formerly obese patients looked like other thin people, they were indeed different. In fact, the researchers found that metabolically the patients resembled people who were starving. They also found that these patients were burning 24 percent fewer calories than those who were thin.

Hirsch discovered that the patients who lost a large amount of weight had to devote their lives to maintaining their weight loss. The patients had to continue to stay in a permanent state of starvation.

Researcher Dr. Ethan Sims tested another theory--that getting fat would render a person vulnerable to an "irreversible condition" of starvation. That theory was proved wrong when Sims studied thin prisoners who volunteered to gain 20 to 25 percent of their weight on purpose. Some inmates were eating 10,000 calories a day. After they gained weight, however, they returned to their normal weights with ease. 

Kolata wrote about another researcher's findings concerning the link between nature and nurture and obesity. Dr. Albert Stunkard studied identical twins and obesity and found that "70 percent of the variation in people's weights  can be accounted for by inheritance." 

Now another finding on the inheritance of obesity has been published by the Los Angeles Times. Two hundred scientists from 5 continents met this summer to study the effects that common chemicals can have on fetal development. The scientists, including pediatricians, epidemiologists and toxicologists, warned that long-term harm from toxic exposures in the womb can lead to a wide range of health problems later in life, including diabetes, prostate cancer, fertility problems, thyroid disorders and obesity. The scientists issued a statement that included an international call to action for revised regulations on chemicals that, even in small doses, can have devastating effects on infant and fetal development. These chemicals include compounds that are found in common plastics, pesticides and cosmetics.

The scientists concluded that, in light of the most recent animal research, "Toxic exposures to chemical pollutants during these windows of increased susceptibility can cause disease and disability in childhood and across the entire span of human life."       

One of the researchers, Dr. Philip Landrigan, said, "A sad aspect with many of these prenatal exposures is that they leave the mother unscathed while causing injury to her fetus." And these altered traits could even be passed on to their children and grandchildren. Timing is recognized to be the most critical element, not necessarily the dosage of the toxic poison. Landrigan said that 80 percent of the major chemicals in commerce today have never been tested to see if they can damage early development.

According to Frederick vom Saal, professor of biological sciences in the Endocrine Disrupters Group at the University of Missouri, when fetuses are exposed to chemicals such as plastics and pesticides in the womb, the way their genes function may be altered to make the child more prone to disease and obesity.    

Vom Saal studied the effects of endocrine-disrupting chemicals including bisphenol-A, a plastic used in toys and resin coatings. He claims that there is an association between increased bisphenol-A use and the obesity surge. Vom Saal's mice that were exposed to endocrine-disrupting chemicals were born with very low birth weights, and the mice gained abnormally large amounts of weight in a very short time, essentially doubling their weight in a week. These mice were obese throughout their lives. Vom Saal claims that low-birth-weight children have been shown to have a similar overcompensation after birth, which leads to obesity throughout their lives. People who have abnormal metabolic systems must essentially live on guard because those systems are misfunctioning.

Obesity is not the only price paid for by children who are innocently exposed to gene- and endocrine-disrupting toxic poisons. We are all aware of the price paid by children exposed to lead and mercury during fetal development. But many of us are unaware of the possible link between decreases in testosterone levels and increased instances of lower sperm count, testicular cancer and insulin resistance in men. Some researchers are suggesting phthalates as the culprits.  

Phthalates are commonly found in soaps, plastics and paints. According to Environmental Health Perspectives, phthalates have been correlated with abnormal sperm counts and low testosterone levels, and a recent study has found a 22 percent drop in testosterone levels in men. And men with low testosterone levels develop abdominal obesity and insulin resistance. A National Health and Nutritional Examination Survey from 1999 to 2002 that studied 1451 men found that men with the highest levels of phthalates in their urine had more belly fat and insulin resistance. The researchers said that more than 75 percent of the U.S. population have measurable levels of phthalates in their urine. 

With all of the recent findings, none of us can afford to permit these chemicals to remain in our environment. This is much too great a risk to ourselves and our children's future. And we cannot afford to ignore the efforts of the obese who have tried repeatedly to lose weight without success. The fortunate who have not been exposed to these toxic substances before birth or those who have no weight problems due to their genetic make-up need to change their attitudes towards others who are overweight.

Published: August 07, 2007
Issue: Fall 2007