It seems that many people, including dietetics professionals and other nutrition experts, are unclear about some of the fundamental yet complex concepts behind the influence of dietary macronutrients (ie, protein, carbohydrate, and fat) on appetite regulation. Recent research has begun to unravel some of the more complicated physiological processes of appetite control and regulation generated by hormones such as leptin, ghrelin, and the gut hormone peptide YY3-35. Although the processes by which the macronutrients in our foods influence appetite regulation have been a topic of study for decades, they remain confusing and are often misunderstood. The objective of this article is to define the terminology commonly used to discuss the macronutrients' roles in appetite regulation and to discuss the interrelated concepts and roles of taste, palatability, and energy density.