The Motivation of
Hunger
Hunger is both physiological and
psychological
• When your stomach feels stuffed you
probably do not feel hungry and when your
stomach is empty you probably get that take
me to McD’s feeling.
• Researchers used to believe that the feeling
of hunger comes from our stomach
• To test the theory out, they made some poor
soul swallow a balloon and inflated the
balloon inside of his stomach
Physiology of Hunger
• He felt full for awhile
but eventually felt
hungry again.
• The experiment showed
hunger was partially
related to the stomach.
• Additionally, those with
their stomachs removed
still feel hunger.
• So hunger must be also
related to the brain
The Brain
In the 1960’s it was discovered that hunger
comes from………..
The Hypothalamus
Guides – eating, drinking,
and body temperature
The Hypothalamus & Hunger
• Along the sides of the hypothalamus is the
lateral hypothalamus:
– It’s the “turning on” eating part of your brain
Stimulate the lateral hypothalamus and even
a well fed animal will begin to eat.
Lesion the lateral hypothalamus and even a
starving animal will have no interest in food.
The Hypothalamus and Hunger
• Along the lower middle section of the hypothalamus is
the ventromedial hypothalamus:
– “turning off” eating – off switch
– which depresses hunger –if stimulated you would feel full.
Stimulate the ventromedial hypothalamus
and the animal will stop eating
Lesion the ventromedial
hypothalamus the animal will
continuously want to eat.
How does the hypothalamus work?
• Hypothalamus acts like a thermostat.
• We are meant to be in a certain weight range for
our body or body type
– Set Point Theory
• When we fall below ideal weight (or our set point)
our body will increase hunger and decrease energy
expenditure
– Basic Metabolic Rate (BMR) – the rate your body burns
calories while at rest
• What happens if we go above our set point?
• The hypothalamus tells us to stop eating and raises
our metabolic rate to burn any excess food
Physiology of Hunger…Cont.
• Glucose
– form of sugar that runs through your body – run
low on glucose and you will feel hungry
• Insulin
– hormone that allows our cells to use glucose for
energy or convert it to fat
– when insulin levels go up, glucose levels go down
• Leptin
– protein that is produced by bloated fat cells
which send out a “stop eating” message
– artificially introduced into obese mice caused
reduced eating and weight lose
Environment and Hunger
Externals vs. Internals
• Externals:
– people whose eating and hunger
is triggered more by the presence
of food (sight, sound, and smell)
than internal factors.
• Internals:
– people whose eating and hunger
is triggered by internal cues,
empty stomach, feelings of
hunger
Taste Preferences – can be based on many
things…culture, parents, availability, etc..
Food tastes better and we chew less when
we are hungry (beginning of a meal).
Food tastes worse
and we chew more
when we are not
hungry (at the end
of the meal).
Its weird, the better the food tastes, the
less time we leave it in our mouths.
Culture and Taste
Eating Disorders
Anorexia Nervosa
 An
eating disorder in
which a normal
weight person diets
and becomes
significantly
underweight, yet,
still feeling fat,
continues to starve.
Bulimia Nervosa
 An
eating disorder
characterized by
episodes of
overeating, usually of
high caloric foods,
followed by vomiting,
laxative use, fasting,
or excessive
exercise.
Obesity
Severely overweight
 Often over 100 pounds
above normal weight
 Threatens their health
 Typically have unhealthy
eating habits or may also
be genetically predisposed
to obesity
Are these disorders cultural?
Body Image