Our understanding of the pathophysiology of obesity remains at best incomplete despite a century of research. During this time, two alternative perspectives have helped shape thinking about the etiology of the disorder. The currently prevailing view holds that excessive fat accumulation results because energy intake exceeds energy expenditure, with excessive food consumption being the primary cause of the imbalance. The other perspective attributes the initiating cause of obesity to intrinsic metabolic defects that shift fuel partitioning from pathways for mobilization and oxidation to those for synthesis and storage. The resulting reduction in fuel oxidation and trapping of energy in adipose tissue drives a compensatory increase in energy intake and, under some conditions, a decrease in expenditure. This theory of obesity pathogenesis has historically garnered relatively less attention despite its pedigree. Here, we present an updated comprehensive formulation of the fuel partitioning theory, focused on evidence gathered over the last 80 years from major animal models of obesity showing a redirection of fuel fluxes from oxidation to storage and accumulation of excess body fat with energy intake equal to or even less than that of lean animals. The aim is to inform current discussions about the etiology of obesity and by so doing, help lay new foundations for the design of more efficacious approaches to obesity research, treatment and prevention.
Funding Information:
We thank Claude Bouchard, Christoffer Clemmensen, Jens Juul Holst and Mitchell Lazar for their helpful comments on earlier drafts of this paper. J.L. is supported by the BRIDGE \u2013 Translational Excellence Programme ( www.bridge.ku.dk ) funded by the Novo Nordisk Foundation (grant NNF20SA0064340). The Novo Nordisk Foundation Center for Basic Metabolic Research is an independent Research Center based at the University of Copenhagen, Denmark, and is partially funded by an unconditional donation (grant NNF18CC0034900) from the Novo Nordisk Foundation ( www.cbmr.ku.dk ). Figures were created using BioRender.com .
Publisher Copyright:
© 2024 The Author(s). Obesity Reviews published by John Wiley & Sons Ltd on behalf of World Obesity Federation.