Cephalic Phase in Anorexia Nervosa,Bulimia Nervosa and Obese Binge Eaters

Food stimulation of gastric and pancreatic secretion is classically divided into cephalic, gastric and intestinal phases.

Cephalic phase refers to a simultaneous activation of gastrointestinal motility, gastric acid and pancreatic enzyme secretion ,as well as, release of hormones from the endocrine pancreas which occurs through activation of vagal -efferents as a result of food-related sensory stimuli such as taste and smell prior to nutrient absorption and which coincides with a thermogenic response.

Of the cephalic phase secretions, cephalic phase insulin release (CPIR) has received the most attention, but pancreatic polypeptide (PP) and glucagon responses have also been studied. While the magnitude of cephalic phase insulin release is relatively small (25% above baseline), pancreatic polypeptide increases 100% above baseline. The large magnitude of the PP response makes it a sensitive indicator of vagal activation to food stimuli.

In most experiments, subjects are either exposed to visual and olfactory stimulation by seeing and smelling the food stimulus or are required to perform a modified sham-feed, i.e. to taste, chew and then expectorate the food stimulus.

In general, cephalic phase are thought to be preparatory response before ingestion of food. Because of their small magnitude, the physiological significance of the cephalic phase hormonal responses has been largely discounted. However, there is evidence that experimental prevention of CPIR lead to hyperinsulinemia and hyperglycemia. Therefore, CPIR may contribute to glucose homeostasis /regulation. Moreover CPIR may be an indicator of hunger and could be important for understanding eating disorders.