Recent origin and evolution of obesity-income correlation across the United States

R Alexander Bentley,Damian J Ruck,Paul Ormerod

doi:10.1057/s41599-018-0201-x

R Alexander Bentley, Damian J Ruck + Show 1 more

Open Access

https://doi.org/10.1057/s41599-018-0201-x

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Abstract

From a gene-culture evolutionary perspective, the recent rise in obesity rates around the Developed world is unprecedented; perhaps the most rapid population-scale shift in human phenotype ever to occur. Focusing on the recent rise of obesity and diabetes in the United States, we consider the predictions of human behavioral ecology (HBE) versus the predictions of social learning (SL) of obesity through cultural traditions and/or peer–to–peer influence. To isolate differences that might discriminate these different models, we first explore temporal and geographic trends in the inverse correlation between household income and obesity and diabetes rates in the U.S. Whereas by 2015 these inverse correlations were strong, these correlations were non-existent as recently as 1990. The inverse correlations have evolved steadily over recent decades, and we present equations for their time evolution since 1990. We then explore evidence for a “social multiplier” effect at county scale over a ten-year period, as well as a social diffusion pattern at state scale over a 26–year period. We conclude that these patterns support HBE and SL as factors driving obesity, with HBE explaining ultimate causation. As a specific “ecological” driver for this human behavior, we speculate that refined sugar in processed foods may be a prime driver of increasing obesity and diabetes.

Highlights

In the United States, where adult obesity prevalence rates have been rising since the 1970s (Kranjac and Wagmiller, 2016), about two-thirds of adults are overweight and over 100,000 U.S deaths per year are attributed to obesity (Ogden et al, 2014)
In 2015, over 35% of the population was obese in U.S states where median household incomes were below $45,000 per year, whereas obesity was less than 25% of state populations where median incomes were above $65,000 (Centers for Disease Control and Prevention, 2017c)
By 2015, the correlation was stronger than ever: in states where median household incomes were below $45,000 per year, like Alabama, Mississippi and West Virginia, over 35% of the population was obese, whereas obesity was less than 25% of state populations where median incomes were above $65,000, such as in Colorado, Massachusetts or California

Summary

Introduction

In the United States, where adult obesity prevalence rates have been rising since the 1970s (Kranjac and Wagmiller, 2016), about two-thirds of adults are overweight and over 100,000 U.S deaths per year are attributed to obesity (Ogden et al, 2014). With obesity rates having tripled in many U.S states over the past 25 years, this rise in obesity prevalence has accelerated. Industrially–processed foods have transformed Western human diets in less than a century. Has this made calories and junk food abundant and inexpensive in high-income countries, but there appear to be other effects such as reduction of gut microbiome diversity (Smits et al, 2017; Muscogiuri et al, 2018)

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