Physiologic control of food intake by neural and chemical mechanisms.

Physiologic control of eating involves neural and chemical regulators that may have therapeutic applications in weight control. Information on the nature and quantity of ingested and stored nutrients is relayed to the brain via sensory nerve fibers. This information is integrated at specific centers in the brain, then impulses in motor nerve fibers are discharged leading to initiation or termination of eating. Chemical regulators of eating behavior include gastrointestinal peptides released during digestion, absorbed glucose circulating in the plasma, and the hormonal regulators of glucose metabolism (insulin and glucagon). There is, however, considerable interplay between neural and chemical processes in regulation of food intake. Neural mechanisms are evidently mediated by chemical regulators, because neurotransmitters, including serotonin, allow nerve impulses to cross synapses. In addition, some chemical regulators are concentrated at brain centers that are implicated in regulation of eating behavior. Although some gastrointestinal peptides and serotoninergic drugs have been used to treat obesity, the existence of a complex control system with alternate mediators of food intake suggests that a single therapeutic agent is unlikely to be applied universally to suppress overeating.