Research on biological mechanisms of eating behavior and related disorders, such as obesity and anorexia nervosa, has become a large field of research in the last 15 years. With the discovery of peptides related to hypothalamic control of food intake (e.g. leptin and ghrelin) the search for the biological 'master key' of feeding control was renewed. As a result, mid-20th century biological concepts based on systematic and cybernetic thoughts fell into oblivion. This review highlights discoveries of hypothalamic-controlled feeding and eating behavior with a cybernetic and systematic perspective. Interestingly, older ideas of hypothalamic function offer possibilities for the incorporation of new molecular discoveries into systematic concepts of feeding behavior.