The Persistence of the Thrifty-Gene Hypothesis

I recently had a manuscript accepted arguing for a new paradigm in interpreting malnutrition. Public health nutrition as a field tends to think of undernutrition and overnutrition as two separate problems. For the former, supplementation and fortification of high-yield crop varieties is often held up as the most effective solution. In the latter, physical activity and fruit and vegetable consumption are the buzzwords. My point in the article was that by ignoring the evolutionary underpinnings of any form of malnutrition, namely that our food environments today are nothing like those on which humans evolved to thrive, we risk seeking quick fixes and ignoring the structural determinants which foster poor nutrition across the globe.

Perhaps not a huge surprise, but the points of feedback I received from reviewers were to incorporate a section on genome wide association studies (GWAS) and a specific section on the "thrifty gene hypothesis." Savannah and I have both briefly commented on this. As a very short run-down, it is the idea that high prevalence of diabetes among indigenous peoples can be effectively explained by a genetic predisposition to store fat. With the ability to rapidly store fat in times of food surplus, the idea goes, individuals would be more likely to survive during times of famine.

From a scientific perspective, this has been fairly thoroughly debunked. Even at an extremely low selective advantage, a "thrifty gene," if it existed, would have spread through the entire human population. We would all be fat. Moreover, it rests on an assumption about indigenous food culture (Indigenous peoples, either as hunter-gatherers or agriculturalists, could only have lived through periods of feast and famine) that is pointedly wrong.

Where this gets particularly pernicious, however, is when such a hypothesis under the guise of scientific validity is invoked when thinking about social policy. Travis Hay details how Canadian policy and programming on indigenous health remains wedded to this idea. He quotes Tallbear, who argues that it is tremendously “important to look back at how [Indigenous] bodies have been treated historically, for knowledge-producing cultures and practices that shaped earlier research and continue to influence the way science is done today." Without this perspective, public health and social policy will mistakenly attribute health disparities among indigenous populations not to larger social determinants of health, e.g. food environments, healthcare access, and social stressors, but to something "wrong" in their genetic code. 

I'm still working out how best to incorporate this into my revise and resubmit, given that it misses the larger point of my paper. And that then gets me thinking about what sorts of references I can provide in an anthropology paper, vs. a (broadly) nutrition focused journal. How much does what passes as "scientific evidence" vary between disciplines and journals? For now, I am grateful to the work of Nancy Krieger and trailblazing that she has done in developing an "ecosocial" theory of health. Her book should be required reading for anyone interested in health at large; unfortunately it's currently relevant for only a small subsection of public health.