ABSTRACT
Intricate behavioral, metabolic, and neuroendocrine mechanisms have evolved to integrate energy intake and dissipation. A delicate balance between intake and expenditure of energy is required to maintain healthy weight. The adaptations that defend against weight loss eventually become maladaptive when obesity and its related metabolic and cardiovascular complications supervene. Hunger is the physiological response to appetite, whereas meal termination occurs in response to satiety signals. The exact mechanisms controlling the primal instincts of appetite and hunger are not understood precisely. The hypothalamus integrates diverse signals, including brain neurotransmitters, peripheral neurohumoral afferents, adipocyte-derived signals, gastrointestinal peptides, and other afferent inputs, to regulate energy homeostasis. The hypothalamic orexigenic signals include neuropeptide Y, agouti-related protein, and the hypocretins/orexins. There is a mature and growing literature on the roles of several adipocyte products, including nonesterified fatty acids, adipocytokines, and leptin, in the regulation of metabolic fuel economy, energy balance, glucoregulation, food intake, and body weight.
