Publisher Summary There are complex neuropeptide-based neural networks that are able to gauge the energy status of the organism and to adjust foraging and eating behavior accordingly. This network is constructed of hypothalamic neuropeptides, such as hypocretin/orexin, neuropeptide Y and agouti-related peptide, α-melanocyte-stimulating hormone, and melanin-concentrating hormone; regulatory circuits that are controlled by peripheral signals of lipid status, such as leptin; gastrointestinal hunger hormones, such as ghrelin; as well as more direct metabolic effects on the hypothalamus that are not as well understood. Often missing from the discussion of energy balance dynamics are the evolved psychological processes that mediate achieved/achieving homeostasis—the nature of the feelings of hunger in the brain, and the large variety of ways the pleasures and displeasures of taste can promote or hinder appetite. This is in addition to the many ways feeding behavior can be disrupted which have no relevance for the normal mechanisms of energy balance regulation. For instance, hunger makes sweetness taste more pleasant, and satiety makes the same sensation feel less pleasant. This chapter briefly focuses on the latter factors, since they need to be considered more closely as investigators search for medicinal agents that may help humans better regulate their weight. It should be noted that considerable progress is being made in understanding how the brain codes taste qualities in both animals and humans, but little of that work has yet been related to our understanding of appetite control agents.