Are We Entering an Epigenetic Spiral of Obesity?
The facts are telling.
Thirty-four percent of American adults aged twenty years or older are obese. In 1996, no state had an obesity rate above 20%. In 2010, no state had an obesity rate below 20%. There's no doubt that the American public's collective girth is growing, and growing fast.
How and why is this happening? Theories abound, some incredibly convincing, but nobody can precisely pinpoint the cause of our portly plight. And the people who say they have the definitive answer are almost always selling something.
Over the past three decades, we've seen a convergence of situations that is driving obesity sky high. Computers have shifted the workforce out of manufacturing lines and into desk chairs. New technologies have transformed our hobbies from the physical to the virtual. Food -- and fast food -- is readily available. The consumption of fast food quadrupled between 1977 and 1995, and agriculture subsidies mean that food is cheaper and more abundant than ever before. This is just a smattering of causes; I'm sure you can add more.
Unfortunately, many of these trends aren't likely to change anytime soon, potentially bringing another factor into play: genetics. The relatively new fields of epigenetics and nutrigenomics are showing that changes in gene expression can be produced by environmental mechanisms. Could rising levels of obesity alter our genes, and, in turn, could these obesity-favoring alterations be passed on to future generations?
Recent animal research shows that it's certainly possible. A 2009 study from the University of Pennsylvania linked a mother rodent's diet-induced obesity to offspring adiposity, risk of cardiovascular disease and impaired glucose metabolism. This research was reaffirmed in 2010 when a study published in Nature showed that obesity can alter gene expression in lab rats, and these changes can then be passed on to progeny. Descendants of rat parents fed an obesity-triggering diet were born with impaired insulin production.
An obese mouse. (But could this same situation happen in humans? As our society rapidly becomes more obese via lifestyle and dietary changes, will we enter a genetic spiral of obesity? Let's turn to Randy Jirtle, director of the Laboratory of Epigenetics and
Imprinting at Duke University, for an answer:
"There is already evidence that epigenetic transgenerational inheritancecan also occur in humans in response to food supply and smoking. Nevertheless, until the epigenetically changeable targets in humans are defined, it
will not be possible to determine if such associations are directly
mediated by epigenetic changes..."
