Why does metabolic rate scale with body size?

Abstract

A long-standing problem has been the origin of quarter-power allometric scaling laws that relate many characteristics of organisms to their body mass^1,2 — specifically, whole-organism metabolic rate, B = aM^b, where M is body mass, a is a taxon-dependent normalization, and b ≈ 3/4 for animals and plants. Darveau et al.³ propose a multiple-cause model for mammalian metabolic rate as the “sum of multiple contributors”, B_i, which they assume to scale as B_i = $a_i{\mathrm{MML:M}}^{b_i}$, and obtain b ≈ 0.78 for the basal and 0.86 for the maximally active rate, ${\mathop V\limits^{\bullet}}{}_{{\rm O}_2}^{\max}$. We argue, however, that this scaling equation is based on technical, theoretical and conceptual errors, including misrepresentations of our published results^4,5.