More to Obesity than Overeating?
Consuming more calories than those expended leads to weight gain. Even more obviously, this knowledge, however valid, has not prevented increasing prevalence of overweight and obesity in the modern world.
Strong evidence suggests obesity may be programmed for some people from even before the moment of birth. Extremely high birth weight infants are more likely to be obese as adults. It has been known for some time that low birth weight babies are also likely to grow up to be obese adults. We need an explanation for this. The new thinking is that our genes can be reprogrammed in fetal life in ways that persist through life and from more causes than undernourished fetuses can account for.
Experiments have recently shown that at least some of the many chemicals to which modern humans are exposed also change life long gene expression with the same result as early fetal caloric deficits. An early definite test of this idea started with bisphenyl A, the monomer of common polycarbonate plastic. A monomer is the simple chemical that polymerizes (combines with itself) making the very long molecules of the finished plastic. Polycarbonate is the plastic most widely used for bottled water containers. A fraction of one part per billion of the monomer fed to pregnant mice resulted in normal seeming infant mice, all of which became obese adult mice. Similar concentrations of bisphenyl A are found in water exposed to polycarbonate plastic. Presumably more of these results will be obtained with many other endocrine disrupting chemicals that have been released in large amounts into our environment since the 1930s such as waste poly chlorinated biphenyls and many intentional components of industrial cleaners, pesticides, herbicides, solvents, dyes, to name a few.
The unprecedented 20% incidence of obesity in modern American children is remarkably close to the incidence of 25% of American pregnancies occurring in smokers who did not stop nicotine use during pregnancy. Miniscule amounts of nicotine comparable to the blood levels of nicotine in even very moderate smokers were fed to pregnant rats resulting in apparently normal young rats, but 100% of them became obese as adult rats--again on a normal diet for rats that did not result in obesity in the control group of rats not exposed to nicotine. Food availability was not restricted for any of the animals—neither the experimental group nor the control animals (and for the mice mentioned above)..
None of this work has been confirmed in humans. Brace for a flood of experiments testing prevalent endocrine disruptors and other common chemicals introduced into the environment in the last generation or so. Some new and better informed (and more cost effective) efforts to clean up the environment are bound to result—some promptly because of the cautionary principle: potentially very important remedial effort is appropriate before absolute proof of its necessity. Meanwhile, some people, bless their souls, are following dietary suggestions with enough effort to overcome their probably adversely programmed genes.
John A. Frantz, member Green County Health Committee
March 5, 2007
A Lesson in Skepticism
A couple of generations ago a prominent citizen of Monroe was confronted by his frantic wife, “I have heard on the radio that the Martians are invading. What should we do?”
Pearl Guess answered, “Turn off the radio.”
As told by Nate Roth