ABSTRACT
While the human body obeys the law of energy conservation, this alone does not imply that dietary carbohydrate, fat, and protein have contributed equally to the rise in obesity prevalence over the past several decades. Indeed, three scientific models of obesity have implicated each macronutrient as being the prime culprit, but the evidence supporting these models is, at best, mixed and, at worst, demonstrably false. This chapter reviews the concepts of energy balance and macronutrient balance as applied to the human body and presents the evidence for and against three scientific models that alternately place the blame for obesity on each dietary macronutrient. Finally, the chapter discusses putative mechanisms for why obesity prevalence has been increasing despite the likelihood that human body weight is actively regulated by a biological feedback control system.
