The brain receives a large number of signals from the ingestion of food. They provide the brain with information on both the adequacy of energy ingested and the macronutrient composition of the food. From this information brain feeding control systems are able to respond and direct the animal to make appropriate food choices so that both the quantitative (energy) needs as well as the qualitative (nutrient) needs are met. An understanding of brain mechanisms regulating feeding will only emerge if their dual purposes are recognized.