The human obesity epidemic, the mismatch paradigm, and our modern “captive” environment

Abstract

In the distant past obesity in humans was rare and likely caused by metabolic dysregulation due to genetic or disease-related pathology. External factors precluded the ability of most people to overeat or under exert. Socio-cultural obesity came about due to the rareness of obesity and its difficulty to achieve. What is rare becomes valuable and what is difficult to achieve becomes a badge of prestige. The modern human obesity epidemic would appear to represent a third class of obesity: environmental obesity. Much like the captive environments which humans construct for the captive/companion animals in our care, the modern human environment has greatly decreased the challenges of life that would restrict food intake and enforce exertion. And like us, our captive/companion animal populations are also experiencing obesity epidemics. A further concern is that maternal obesity alters maternal signaling to offspring, in utero through the placenta and after birth through breast milk, in ways that perpetuate an enhanced vulnerability to obesity. Molecules such as leptin, produced by adipose tissue and placenta, have significant developmental effects on brain areas associated with feeding behavior. Leptin and other cytokines and growth factors are found in breast milk. These molecules have positive effects on gut maturation; their effects on metabolism and brain development are unclear. Placenta and brain also are hotspots for epigenetic regulation, and epigenetic changes may play significant roles in the later vulnerability to obesity and to the development of a diverse array of diseases, including heart disease, hypertension, and noninsulin-dependent diabetes. Am. J. Hum. Biol. 00:000-000, 2012.

From Passive Overeating to “Food Addiction”: A Spectrum of Compulsion and Severity

“…Research has also focused on the complex interaction between the “human epigenome” and the modern food supply. For instance, there is accumulating evidence that maternal body weight and diet may work, via in utero placental signaling, to alter her offspring's future eating behavior and risk for obesity [4]. …”

“…Regulatory or homeostatic systems evolved to respond to challenges to the normal “evolutionary experience” of the organism and to make suitable compensatory adjustments [4]. When any homeostatic system remains chronically activated, or activated to a level outside its norm due to persistent external pressures, it will eventually sustain damage or long-lasting alterations in the related physiology [4].…”

“…A biocultural viewpoint, highlighting co-evolutionary processes, is, undoubtedly, the best viewpoint for understanding these issues [26]. Since such a rapid and recent change in the population phenotype could not be genetic, one must assume that our current environment interacts with our evolved biology, in some complex way, to give rise to the situation where a substantial proportion of the population are prone to persistent weight gain [4]. …”

Differences in Food Environment Perceptions and Spatial Attributes of Food Shopping Between Residents of Low and High Food Access Areas

“…4,5 US policymakers have questioned the extent to which healthy foods are easily accessible and available. 6 The US Department of Agriculture Economic Research Service (ERS) has reported that limited access to major food outlets such as grocery stores and supermarkets affects over 23.5 million people living in 6,529 different Census tracts. 7,8 In an updated USDA ERS report based on 2010 Census and supermarket data, this statistic increased to 29.7 million people, who lived in a low-income area more than 1 mile from a supermarket.…”

Brazilian Undergraduate Students’ Conceptions on the Origins of Human Social Behavior: Implications for Teaching Evolution

“…Our innate preferences for sweet, soft and hot food-inherited from our ape common ancestors (Wrangham 2009)-led to substantial increase in the fat and carbohydrate composition of human diet in association with a reduction in the energy expenditure associated with food collection (Bellisari 2008;Power and Schulkin 2009;Cordain et al 2005). Those cultural changes happened far too quickly to be accompanied by evolutionary (genetic) changes leading to increased rates of overweight and obesity (Power 2012). The worldwide increase in obesity thus represents an excellent opportunity to discuss the mutual influence of the nature and nurture factors on a topic that is both socially and biologically relevant.…”