Reprod. Nutr. Dev. 45 (2005) 129-142
DOI: 10.1051/rnd:2005014

Contributing factors and variability of energy expenditure in non-obese, obese, and post-obese adolescents

Michel Vermorel^a, Stefano Lazzer^b, Abdelali Bitar^c, Jérôme Ribeyre^d, Christophe Montaurier^b, Nicole Fellmann^d, Jean Coudert^d, Martine Meyer^e and Yves Boirie<sup>b

a</sup>  Energy and Lipid Metabolism Research Unit, INRA, Theix, 63122 St-Genès-Champanelle, France
^b  Energy and Protein Metabolism Research Unit, INRA, University of Auvergne, CRNH, 63001 Clermont-Ferrand, France
^c  Department of Biology, Applied Physiology Laboratory, Faculty of Sciences, El Jadida, Morocco
^d  Physiology and Sports Biology Laboratory, Medical Faculty, 63001 Clermont-Ferrand, France
^e  Hôtel-Dieu Pediatric Hospital, Human Nutrition Research Centre in Auvergne, 63001 Clermont-Ferrand, France

(Received 9 August 2004; accepted 5 January 2005)

Abstract - Energy expenditure (EE) is a major determinant of energy balance and body composition. The objectives of this paper were to review the contributing factors of the main components of daily EE (DEE) and the inter-individual variability in these components in non-obese (NOb), obese (Ob), and post-obese (POb) adolescents. Body composition especially fat-free mass (FFM), is the major determinant of the basal metabolic rate which contributes 50-70% of DEE, whereas fat mass (FM) is a significant factor only in obese subjects. Physical activity is the second main variation factor of DEE, whereas growth, the thermic effect of food, and thermoregulation are generally of marginal importance. The energy costs and EE associated with various sedentary and physical activities were assessed in NOb, Ob and POb subjects both in standardised and in free-living conditions. The inter-individual variability of DEE is high, even after adjustment for body composition, mainly because of great differences in time devoted to the various physical activities. DEE and EE associated with sleep and sedentary activities are significantly higher in Ob than in NOb, but not after adjustment for FFM. On the contrary, EE associated with physical activities is not significantly different between Ob and NOb adolescents, but 61% lower in Ob subjects after adjustment for body composition. Multidisciplinary weight-reduction programmes including moderate energy restriction and physical training result in great FM loss, maintenance of FFM, improvement of physical capacities, but reductions in organ and tissue metabolic rate and in EE associated with the various sedentary and physical activities, which may favour body weight regain in the less active POb subjects.

Key words: body composition / basal metabolic rate / physical activity / thermoregulation

Corresponding author: Michel Vermorel vermorel@clermont.inra.fr

© INRA, EDP Sciences 2005