AUTHOR=Even Patrick C. TITLE=Body size, spontaneous activity and thermogenesis effects on energy expenditure: an introduction to a topic on energy metabolism JOURNAL=Frontiers in Physiology VOLUME=4 YEAR=2013 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2013.00301 DOI=10.3389/fphys.2013.00301 ISSN=1664-042X