1. ¹Department of Medicine, Obesity Research Center, St Luke's/Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York, NY, USA
2. ²Pediatric Unit, Verona University Medical School, Verona, Italy

Correspondence: Dr SB Heymsfield, St Luke's/Roosevelt Hospital, Weight Control Unit, 1090 Amsterdam Avenue, 14th floor, New York, NY 10025, USA. E-mail: sbh2@columbia.edu

Received 5 May 2003; Revised 26 October 2003; Accepted 17 November 2003; Published online 9 November 2004.

Abstract

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.