The proper understanding of obesity requires a multifaceted approach. Behavioral considerations of eating and activity patterns do not account for the large between- and within-subjects variance associated with the energy-balance equation. Sources of adaptive and dispositional variance in metabolic rates are reviewed and suggested to be a likely source of importance for the proper conceptualization and intervention of obesity. Five proposed mechanisms of metabolic variation are reviewed with consideration of the supporting evidence for each mechanism. The generalizability of some of the proposed mechanisms is limited because of the scope of past research. However, the roles of lipoprotein lipase in fat storage and brown adipose tissue in thermogenesis are intriguing possibilities for future research with humans
