With the increasing prevalence of obesity and associated morbidity, research continues to investigate the associated factors as well as approaches for effective bodyweight management. While there is consensus that obesity is characterised by an energy imbalance, the interactions between the various components of energy components and the implications of the homeostatic determinants remain controversial. This review critiques the existing theories on energy balance in relation to the law of thermodynamics and proposes the inclusion of important determinants in the energy balance equation.