Canaries in the coal mine: A cross-species analysis of the plurality of obesity epidemics

Department of Biostatistics, University of Alabama, Birmingham, AL, USA.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 11/2010; 278(1712):1626-32. DOI: 10.1098/rspb.2010.1890
Source: PubMed


A dramatic rise in obesity has occurred among humans within the last several decades. Little is known about whether similar increases in obesity have occurred in animals inhabiting human-influenced environments. We examined samples collectively consisting of over 20 000 animals from 24 populations (12 divided separately into males and females) of animals representing eight species living with or around humans in industrialized societies. In all populations, the estimated coefficient for the trend of body weight over time was positive (i.e. increasing). The probability of all trends being in the same direction by chance is 1.2 × 10(-7). Surprisingly, we find that over the past several decades, average mid-life body weights have risen among primates and rodents living in research colonies, as well as among feral rodents and domestic dogs and cats. The consistency of these findings among animals living in varying environments, suggests the intriguing possibility that the aetiology of increasing body weight may involve several as-of-yet unidentified and/or poorly understood factors (e.g. viral pathogens, epigenetic factors). This finding may eventually enhance the discovery and fuller elucidation of other factors that have contributed to the recent rise in obesity rates.

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    • "not due to eggs or offspring). Some evidence suggests that the average weight of companion animals, laboratory animals and wild animals in anthropogenically disturbed environments has been increasing over time (Klimentidis et al. 2011; Raubenheimer et al. 2015). However, in many natural environments, normal homoeostatic regulation of food and nutrient acquisition would be expected to limit the extent to which animals gain excessive weight or lipid reserves, as will limited availability of food or other constraints on feeding. "
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    ABSTRACT: 1.Body condition indices, measures of body “plumpness” or mass relative to frame size, are often used as a proxy for lipid reserves or fitness-related traits of animals and assumed to be positively related to fitness.2.The quantification and analysis of body condition indices has been the subject of debate for decades. Here we summarize three additional concerns with the use of body condition indices.3.First, body condition index is often poorly correlated with lipid content in animals. Second, even if body condition index and lipid content are correlated, lipid content of an animal may not be the most important aspect of body composition influencing fitness. Finally, neither body condition index nor lipid reserves are likely to be directly positively related to fitness in animals, as many animals homeostatically regulate intermediate levels of condition index or lipid reserves, with both higher and lower values incurring fitness costs.4.A wide range of analytical methods, including some relatively inexpensive and simple measures, are available for more detailed measures of animal body composition or fitness-related traits. Replacing body condition indices with more direct measures of body composition - even relatively simple measures - can inform understanding of the physiological mechanisms underlying animal responses in a wide range of behavioral, ecological and evolutionary studies.This article is protected by copyright. All rights reserved.
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    • "A recent study by Hersoug et al. (2012) proposed that increases in obesity and type-2 diabetes may be due to increased atmospheric carbon dioxide (CO 2 ). This hypothesis was motivated by a finding that animal species living under controlled environments (various laboratory rodents and primates) or near human establishments (cats, dogs, feral urban and rural rats) had significant weight gain over the last 50 years, although those animals have had the same diets for decades (Klimentidis et al., 2011). The documentation of greater average weight in numerous species indicates that there may be an environmental component applicable to all species impacting current trends in body composition. "
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    ABSTRACT: Recent studies suggest that increasing levels of the greenhouse gas, carbon dioxide (CO2), may influence weight gain and thus may play a role in rising trends in obesity and diabetes. We conducted an ecological study to examine the associations between CO2 emissions from fossil fuel combustion and changes in the prevalence of obesity and diabetes in the United States. County-level data on CO2 emissions, prevalence of obesity and diagnosed diabetes, other sociodemographic factors and neighborhood characteristics related to urbanicity, and fine particles (PM2.5) between 2004 and 2008 were obtained from the Vulcan Project, Centers for Disease Control and Prevention, and American Community Survey. Linear mixed effect modeling of 3019 counties for the associations between average CO2 emissions and changes in diabetes and obesity prevalence between 2004 and 2008 was performed. The average obesity and diabetes prevalence increased between 2004 and 2008 by 3.65% (SD: 1.88%) and 1.65% (SD: 1.70%), respectively. A marginally significant positive association between CO2 emission and changes in obesity prevalence was found with adjustment for sociodemographic factors, indicators of urbanicity and spatial autocorrelation (p-trend = 0.06). The association became weaker and nonsignificant with further adjustment for PM2.5 (p-trend = 0.17). There was a significant positive association between CO2 emission and changes in diabetes prevalence before controlling for PM2.5 (p-trend = 0.05) but the association became null after controlling for PM2.5 (p-trend = 0.49), suggesting that PM2.5 is a critical confounder in the association between CO2 emission and changes in diabetes prevalence. This study does not support the hypothesis that CO2 emissions, a leading driver of climate change, may be linked to increasing trends in obesity and diabetes, though there was an indication of possible link between CO2 and obesity.
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    • ") – a vanishingly small possibility that this is a chance occurrence ( Klimentidis et al . , 2011 ) . The most reasonable conclusion is that something has changed in the dwell - ing environment of these animals , making them obese in parallel with humans ."
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