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Low physical activity levels of modern Homo sapiens among free-ranging mammals


Obesity prevalence rates are increasing worldwide and one prevailing hypothesis is that physical activity levels of modern humans are markedly reduced compared to those of our Paleolithic ancestors. We examine this hypothesis by deriving relative activity energy expenditure from available doubly labeled water and indirect calorimetry data in free-ranging non-human mammals. Our results, given the constraints posed by limited data availability, suggest that a low physical activity level, much less than that observed in free-ranging non-human mammals or highly active humans, is present in modern adult humans living within advanced settings. Our observations lend support to the hypothesis that low activity-related energy expenditure levels contribute to the rising worldwide prevalence of obesity.

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We acknowledge the new primate doubly labeled water data generously provided by Jeanne and Stuart Altmann of Princeton University.

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Correspondence to S B Heymsfield.

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Supported by National Institutes of Health Grant RO1-NIDDK 42618.


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Appendix A1

Free-ranging expenditure was evaluated using a composite database developed from previously reported and new doubly labeled water human and animal studies (see Table A1).

Table A1 Field and resting energy expenditure data in mammals

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Hayes, M., Chustek, M., Heshka, S. et al. Low physical activity levels of modern Homo sapiens among free-ranging mammals. Int J Obes 29, 151–156 (2005).

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  • energy expenditure
  • physical activity
  • doubly labeled water
  • resting energy expenditure

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