The eating paradox: How we tolerate food.

Abstract

It is hypothesized that food, which is certainly a necessary commodity with powerful positive reinforcing qualities, also provides a potential threat to organisms, including humans. The act of eating, although necessary for the provision of energy, is a particularly disruptive event in a homeostatic sense. Just as humans learn responses to help them tolerate the administration of dangerous drugs, so do they learn to make anticipatory responses that help minimize the impact of meals on the body, to limit the amount of food consumed within any individual meal, to recruit several parts of the protective stress-response system while meals are being processed, and to limit postprandial behaviors so as to minimize the possibility of disrupting homeostatic systems even more. It is further hypothesized that defenses against eating too much may become activated inappropriately and contribute to clinical problems such as reactive hypoglycemia.

Anticipatory physiological regulation in feeding biology: Cephalic phase responses

“…Meals result in perturbations of the internal milieu that must be accommodated (Woods, 1991); the nutrients that enter the blood in pulses from the digestive tract during feeding must be metabolized or transported to and sequestered in the appropriate storage pools. Later, when the gastrointestinal tract is largely empty, nutrients reenter the blood from nutrient stores.…”

“…They prepare the organism to assimilate the ingested nutrients. This is a key adaptation, as although feeding is necessary for survival, it also presents a significant challenge to homeostasis, in what has been termed the paradox of feeding (Woods, 1991).…”

“…Starting from the work of Claude Bernard (1865) to Walter Cannon (1935) to modern physiology, the concept that stability of the internal milieu is required for health and survival has been a central tenet. Woods (1991) presented the fundamental paradox of feeding from this physiological perspective. Organisms must consume food in order to survive.…”

“…Cephalic phase responses have been suggested to play a role in appetite and satiety (Powley, 1977;Woods, 1991). Palatable foods generally result in more robust cephalic phase responses than do less preferred foods.…”

“…Palatable foods generally result in more robust cephalic phase responses than do less preferred foods. Preventing cephalic phase responses results in animals and humans eating smaller meals (reviewed in Woods, 1991). This is an example of the short-term effects of cephalic phase responses and the role of defense of homeostasis in appetite and satiety.…”