Recently, I saw a segment on The Daily Show with Jon Stewart about a baby who had been denied health insurance for being in the 99th percentile for his weight class; in other words, too fat. Immediately I was appalled at the ridiculousness of this, not just in that it feels horrible, but because I felt quite certain to recall that one’s weight early in life (birthweight through the first year) was inversely correlated with the likelihood for health disorders later in life.
What I was remembering was a theory known as the thrifty phenotype hypothesis. This theory posits that the relationship between low birth weight and subsequent health risks observed later in life could be explained by epigenetic programming that may be the result of adaptation to environmental conditions.
I scrounged around the back-up of my old hard drive and located a paper I wrote on the topic for a neural development course, in it I wrote:
The plasticity of a developing phenotype demonstrates in many ways that when an organism encounters an experience, prenatally or postnatally, the traits that emerge are seen as those that will enable the organism to encounter the same or similar experiences throughout its life. Gottlieb (2002) posits that as these traits manifest developmentally, those that best suit the organism for environmental demands are selected for, thus explaining the spread of similar epigenetic programming patterns… However, Meaney, Szyf and Seckl (2007) note that these adaptive traits are not selected for the longevity of the organism, just reproductive health. As is the case, a phenotype that might be advantageous to a developing organism early in life may involve characteristics harmful to the organisms later in life.
Meaney, Szfy and Seckl (2007) go on to discuss what is known as the “thrifty phenotype hypothesis.” Taking that the developing organism will select traits based on experience to construct a phenotype suited for the environment, factors such as stress would influence development to accommodate for the expectation of continued adversity. The thrifty phenotype hypothesis posits that an organism of low birth weight would be better suited for an environment with scarce food supply or high metabolic (stressful) strain. As stated earlier, natural selection is not a mechanism to ensure a long and healthy life for the organism, but to serve reproductive needs… When the organism ‘expects’ adversity, the goal becomes to minimize metabolic needs (low birth weight) and accelerate the onset of reproductive behaviors.
All the skepticism in the world does not inoculate one from drawing the occasional bad inference now and again. For one, I mistook this literature research in an undergraduate course to offer me some kind of insight about the relationship of infant weight and health. And second, low birth weight is not the same as low infant weight, and heavy infant weight is not necessarily the opposite thereof. Upon deciding to write up a Gotham Skeptic post expressing my outrage about baby Alex, a preliminary search of the medical literature revealed that my points were weak, misguided and that it was not quite so easy a task to sift through the data.
For one thing, development research is several steps away from a true experiment. You cannot randomly select and assign fetuses to be born low birth weight, control for all environmental variables for the first 10-20-30 years of his/her life just so you can observe variation in your dependent measures related to obesity, hypertension and blood pressure in adulthood. Therefore, the research is an observational, and at best correlational, longitudinal investigation with a myriad of extraneous variables contaminating whatever unambiguous interpretation of the results you may have hoped for.
This is not to mention that fact that there were many published studies that did not support this hypothesis, including a study demonstrating that infant weight is not significantly related to adolescent weight, another showing that maternal weight is a better predictor of obesity in adulthood, and another showing that rapid weight gain early in life (heavy infant weight) does predict health problems later in life.
In addition, even if high birth weight did demonstrate protective developmental effects on health in adulthood, this does not necessarily indicate that heavier weights during infancy are without health complications in the present and immediate future. It would be unlikely for an insurance company to cover an infant through adulthood, so rejecting or accepting Alex based on the risk assessment of preexisting conditions wouldn’t involve projections that far in the future.
In short, there was no clear cut criticism of the health insurance companies initial decision, at least not one that was as well supported by the medical research as I had initially believed. While one could (and I certainly would) still argue that the decision was morally reprehensible, it could not be proven empirically unsound.
But, this experience did teach me quite a bit about skepticism, both my own and in general. Despite my initial conclusions and criticisms, I still did what any skeptic worth her weight in salt would do- I turned to the primary literature. More so, instead of cherry picking results that support my initial conclusions, or that generalize about such findings, a skeptic will not ignore the empirical evidence.
Being wrong about something, anything, is part of being a human. Taking it as an opportunity to explore a topic in more depth and see where the data takes you, that’s being a skeptic.
