ABSTRACT
Humans and most other living creatures have evolved in environments where food has only been occasionally available. In this context it is understandable that evolutionary selection pressure has favored those individuals who have been able to eat and store as much energy as possible once available. Vast energy stores founded during periods of plenty subsequently served as supplementary calories during periods where food was scarce, enabling women of childbearing age to sustain both pregnancy periods and breast-feeding. Such evolutionary advantages are detrimental in environments where food is never scarce and our current fight against obesity is to a large extent a result of genetic background. Hence it should come as little surprise that a thorough understanding of the expression regulation and function of gene products involved in energy homeostasis is fundamental in our mapping of pathways governing body weight. The brain has a central role as homeostatic device integrating external and internal sensory information for the purpose of keeping physiological variables within narrow limits. Body energy depots are among such regulated variables, and the major central nervous system (CNS) sites involved in this regulation are hypothalamus and lower brainstem areas receiving visceral sensory afferents.
