Module 34 – Hunger (an example of motivation)

 

What causes us to feel hungry?

Physiological Factors:

 

The role of stomach contractions was investigated.    Is hunger the result of the pangs of an empty stomach?  Washburn and Cannon (1912) did research where the subject swallowed a ballon that measured stomach contractions.  While being monitored, he pressed a key each time he felt hungry.  The discovery: There were stomach contractions whenever he felt hungry.  (Note: some diet aids try to reduce the feeling of an empty stomach by filling it with indigestible fibers that absorb water or eating high volume of low calories food and limiting other intake.  With gastric bypass surgery, the smaller remaining stomach produces less ghrelin – see below.) 

 

 

 

However, other research has shown that hunger persists even when the stomach is removed (due to ulcerated or cancerous stomach in humans or stomachs removed in rat studies).  So there are other factors.

 

 

You can feel hungry on a full stomach!  So what else contributes to the physiological aspects of hunger?

 

Hunger’s inner push primarily originates not from the stomach’s contractions but from variations in body chemistry, including hormones that heighten or reduce hunger.  People and animals automatically regulate their caloric intake to prevent energy deficits and maintain a stable body weight (homeostasis).  The body has mechanisms to keep tabs on its resources and current status:

 

 

 

 

 

 

 

Psychological / Emotional / Social Factors

Our eagerness to eat is pushed by our physiological state – our body chemistry and hypothalamic activity.  Yet there is more to it.  Rozin (1998) demonstrated that two patients with amnesia who had no memory of recent events, would eat a second and a third meal offer 20 minutes after the previous one was finished.  This suggests part of knowing when to eat is our memory of our last meal.  We anticipate eating again and start feeling hungry.

 

Taste Preference:  As our hunger diminishes, our eating behavior changes.  We tend to eat faster when we are hungrier.  Our taste preferences for sweet and salty tastes are genetic.  Other taste preferences are conditioned. 

Food aversions can also be learned.  We have a natural dislike or reluctance to eat things that are unfamiliar to us.  Culture influences what is “normal” – North Americans eat beef, Hindus would not think of it.  Dog, rat and horse meat are desirable in some parts of the world.  We would not think of eating them!

 

 

Eating Disorders

 

 

 

Women’s Body Images

 

 

Fallon and Rozin (1985) in a study of 500 university women found that not only that women’s “ideal body weight” was less than their current weight, but that the weight that they thought men preferred was less than the weight men actually preferred.

 

Body ideals vary across culture and time.  In places where disease is a problem (like much of Africa), bigger is better.  Thinness = poverty, hunger in this cultures experience.

 

In Western cultures, the rise in eating disorders coincides with an increase over the last 50 years in women having poor body image.  It is a complex recipe of cultural pressure to be thin, added to low self-esteem and negative emotions (perhaps genetically predisposed) and mixed with stressful life experiences.  Eating disorders are multiply determined biopsychosocial disorders!