title: Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans.
abstract: Current obesity prevention strategies recommend increasing daily physical activity, assuming that increased activity will lead to corresponding increases in total energy expenditure and prevent or reverse energy imbalance and weight gain [1-3]. Such Additive total energy expenditure models are supported by exercise intervention and accelerometry studies reporting positive correlations between physical activity and total energy expenditure [4] but are challenged by ecological studies in humans and other species showing that more active populations do not have higher total energy expenditure [5-8]. Here we tested a Constrained total energy expenditure model, in which total energy expenditure increases with physical activity at low activity levels but plateaus at higher activity levels as the body adapts to maintain total energy expenditure within a narrow range. We compared total energy expenditure, measured using doubly labeled water, against physical activity, measured using accelerometry, for a large (n = 332) sample of adults living in five populations [9]. After adjusting for body size and composition, total energy expenditure was positively correlated with physical activity, but the relationship was markedly stronger over the lower range of physical activity. For subjects in the upper range of physical activity, total energy expenditure plateaued, supporting a Constrained total energy expenditure model. Body fat percentage and activity intensity appear to modulate the metabolic response to physical activity. Models of energy balance employed in public health [1-3] should be revised to better reflect the constrained nature of total energy expenditure and the complex effects of physical activity on metabolic physiology.
authors.affiliation: Department of Anthropology, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10065, USA; New York Consortium for Evolutionary Primatology, New York, NY 10065, USA. Electronic address: herman.pontzer@hunter.cuny.edu.
authors.forename: Herman
authors.initials: H
authors.lastname: Pontzer
authors.affiliation: Public Health Sciences, Stritch School of Medicine, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA.
authors.forename: Ramon
authors.initials: R
authors.lastname: Durazo-Arvizu
authors.affiliation: Public Health Sciences, Stritch School of Medicine, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA.
authors.forename: Lara R
authors.initials: LR
authors.lastname: Dugas
authors.affiliation: Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
authors.forename: Jacob
authors.initials: J
authors.lastname: Plange-Rhule
authors.affiliation: Institute of Social & Preventive Medicine, Lausanne University Hospital, Rue de la Corniche 10, 1010 Lausanne, Switzerland; Ministry of Health, PO Box 52, Victoria, Mahé, Seychelles.
authors.forename: Pascal
authors.initials: P
authors.lastname: Bovet
authors.affiliation: UWI Solutions for Developing Countries, The University of the West Indies, 25 West Road, UWI Mona Campus, Kingston 7, Jamaica.
authors.forename: Terrence E
authors.initials: TE
authors.lastname: Forrester
authors.affiliation: Research Unit for Exercise Science and Sports Medicine, University of Cape Town, PO Box 115, Newlands 7725, Cape Town, South Africa.
authors.forename: Estelle V
authors.initials: EV
authors.lastname: Lambert
authors.affiliation: Public Health Sciences, Stritch School of Medicine, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Cooper
authors.affiliation: Nutritional Sciences, Biotechnology Center, University of Wisconsin-Madison, 425 Henry Mall, Madison, WI 53705, USA.
authors.forename: Dale A
authors.initials: DA
authors.lastname: Schoeller
authors.affiliation: Public Health Sciences, Stritch School of Medicine, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Luke
mesh_terms: D061725:Accelerometry; D000064:Acclimatization; D000328:Adult; D000349:Africa; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009043:Motor Activity; D014481:United States
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