The Psychology of Eating: From Healthy to Disordered Behavior

Food Choice 51

who became obese. Research has since been carried out using a number
of methods, including experimentally induced lesions to the hypothalamus
in animals, investigations of changes in feeding after damage to specific sites
in the brain, the effects of neurotransmitters introduced into discrete parts
of the brain, the impact of drugs (recreational and medicinal) on feeding,
and the use of functional magnetic resonance imaging (fMRI).
Early studies proposed a simple model of feeding and indicated that the
hypothalamus was central to food intake, with the medial hypothalamus
being the satiety centerand the lateral hypothalamus being the feeding
center. More recently, researchers have proposed a more complex approach
to understanding feeding and have developed a hierarchical model which
emphasizes the hypothalamus as important, but also highlights a role for
numerous other brain regions. From this perspective, the regions of the
brain most closely linked with feeding are the paraventrial hypothalamus
and the perifornical area. Central to both the simple and more complex
models, however, are a number of neurotransmitters which are regarded
as key to our understanding of the neurobiological basis of eating behavior.
The psychophysiology of food intake highlights the role of three main
neurotransmitters that influence appetite and are situated in either the
central nervous system or the peripheral nervous system. These neuro-
transmitters are the catecholamines, serotonin, and the peptides. These will
now be considered in terms of those that increase food intake and those
that decrease it.

Neurotransmitters that increase food intake
A number of neurotransmitters are associated with an increase in eating
behavior:

• Norepinephrine (NE): This catecholamine was the first neurotransmitter
  to be linked with eating behavior. Research indicates that injections
  of NE into the hypothalamus can stimulate feeding if injected into the
  paraventricular nucleus and can reduce feeding if injected into the
  perfornical area of the hypothalamus. Studies also show that the injec-
  tion of NE is most effective if given at mealtimes. Leibowitz (1986)
  has carried out research in this area and suggested that NE may not
  only increase calorie intake but also trigger a specific desire for
  carbohydrate intake.


• Neuropeptide Y: This is a 33-amino-acid peptide, and high concentra-
  tions of it are found in the paraventricular hypothalamus and the