When you have a few spare minutes on your lunch break, walk by the grade school playground in your neighborhood. Even at a quick glance you will notice that almost all the children are in motion – running, chasing, or being chased. Don’t linger too long or make repeat visits because unfortunately your presence may raise suspicions about your motives. But, even on your brief visit, you will also notice that there are a few children who are sitting down either chatting with a classmate or playing by themselves. If despite my caution you returned several days in a row, you would have noticed that the sedentary outliers tend to be the same children.
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Some of the children playing alone simply may be shy loners or socially inept. But I’ve always suspected that there are some people who come in the world genetically predisposed to being sedentary. You can try to make the environment more enticing and stimulating, but the children predestined to be inactive will choose to sit and watch. Not surprisingly, most of those less active children are predestined to be overweight and obese.
At least as young children we seem to be driven to be active, and it is the few outliers who are sedentary. A recent investigation from the department of health and kinesiology at Texas A&M University at College Station is beginning to shed some light on when in our evolutionary history the urge to be active was incorporated into our genome (PLOS ONE. 2019 Apr 29. doi: 10.1371/journal.pone.0216155). The researchers found that snippets of DNA already known to be associated with levels of activity emerged in our ancestors before we were Homo sapiens about 500,000 years ago. This finding surprised the investigators who had suspected that this incorporation of a gene sequence driving activity was more likely to have occurred ten thousand years ago when subsistence farming and its physical demands first appeared.
The authors now postulate that the drive to be active coincided as pre–Homo sapiens grew larger and moved from a treed landscape into the open savanna (“To Move Is to Thrive. It’s in Our Genes” by Gretchen Reynolds. The New York Times, May 15, 2019). As J. Timothy Lightfoot, the senior investigator, observed, “If you were lazy then, you did not survive.”
Our observation of a playground in contact motion is probably evidence that those snippets of DNA still are buried in our genome. However, it is abundantly clear that in North America one doesn’t need to be active to survive, at least in the sense of being reproductively fit. It only takes a few us who must be physically active to grow and build things that we in the sedentary majority can buy or trade for.
There are some of us who have inherited some DNA snippets that drive us to be active post early childhood. My father walked two or three times a day until a few months before his death at 92, and not because someone told him it do it for his health. Like him, I just feel better if I have spent a couple of hours being active every day.
Dr. William G. Wilkoff
The challenge for us as pediatricians is to help families create environments that foster continued activity by discouraging sedentary entertainments and modeling active lifestyles. For example, simple things like choosing a spot at the periphery of the parking lot instead of close to the store. Choosing stairs instead of the elevator. Of course, anything you will be doing is artificial because the truth is we don’t need to be active to survive even though the urge to move is deeply rooted in our genes.
Dr. Wilkoff practiced primary care pediatrics in Brunswick, Maine for nearly 40 years. He has authored several books on behavioral pediatrics, including “How to Say No to Your Toddler.” Email him at pdnews@mdedge.com.