Hunger
The Physiology of Hunger
• Contractions of the stomach
–Washburn study
Physiology of Hunger
• Washburn’s studies
showed hunger was
partially related to the
stomach.
• But those with their
stomachs removed
still feel hunger.
Body Chemistry
• Glucose
• The hormone
insulin converts
glucose to fat.
• When glucose
levels drop- hunger
increases.
The Physiology of Hunger
Body Chemistry and the Brain
• Glucose
• Insulin
• Hypothalamus
–Lateral hypothalamus
• orexin
–Vetromedial hypothalamus
The Brain
In the 1960’s it was discovered that hunger
comes from………..
The Hypothalamus
The Hypothalamus & Hunger
• Along the sides of the hypothalamus is the
lateral hypothalamus: which brings on
hunger.
Stimulate the lateral hypothalamus and even
a well fed animal will begin to eat.
Lesion the lateral hypothalamus and 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: which depresses hunger.
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?
Two Theories
Set Point
Leptin
• Hypothalamus acts like a
• Leptin is a protein
thermostat.
produced by bloated
fat cells.
• We are meant to be in a
certain weight range.
• Hypothalamus senses
rises in leptin and will • When we fall below
curb eating and
weight our body will
increase activity.
increase hunger and
decrease energy
• Can leptin injections
expenditure (Basic
help me?
Metabolic Rate).
• What happens if we go
above our set point?
The Physiology of Hunger
Body Chemistry and the Brain
• Appetite hormones
–Ghrelin
–Obestatin
–PYY
–Leptin
• Set point
• Basal metabolic rate
The Appetite Hormones
• Insulin: Hormone secreted by pancreas—controls blood
glucose.
• Leptin: Protein secreted by fat cells—when abundant,
causes brain to increase metabolism and decrease hunger.
• Orexin: Hunger-triggering hormone secreted by
hypothalamus.
• Ghrelin: Hormone secreted by empty stomach—sends
“I’m Hungry” signals to the brain.
• Obestatin: Sister hormone to ghrelin. Secreted by
stomach—sends “I’m Full” signals to the brain.
• PYY: Digestive tract hormone—sends “I’m Not Hungry”
signals to the brain.
The Psychology of Hunger
Taste Preferences: Biology and Culture
• Taste preferences
– Sweet & Salty: Genetic & Universal
– Neophobia: fear of trying new and
unfamiliar—extends to foods
– Adaptive taste preferences
The Psychology of Hunger
Eating Disorders
• Eating disorders
–Anorexia nervosa
–Bulimia nervosa
–Binge-eating disorder
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.
Eating Disorders
Bulimia Nervosa
• An eating disorder
characterized by
episodes of
overeating, usually of
high caloric foods,
followed by vomiting,
laxative use, fasting,
or excessive
exercise.
Are these disorders cultural?
Body Image
Level of Analysis for Our Hunger
Motivation
Level of Analysis for Our Hunger
Motivation
Level of Analysis for Our Hunger
Motivation
Level of Analysis for Our Hunger
Motivation
Obesity and Weight Control
• Historical explanations
for obesity
• Obesity
– Definition (BMI 30 & ↑)
– Statistics
• Adult obesity, 34%(more
than doubled in last 40 yrs)
• Child-teen obesity has
quadrupled
– Obesity and life
expectancy
Calculate your BMI
Obesity
Obesity
• Severely overweight
to the point where it
causes health issues.
• Mostly eating habits
but some people are
predisposed towards
obesity.
Click on the pictures to see
some case studies on obesity.
Obesity and Weight Control
The Social Effects of Obesity
• Social effects of obesity
• Weight discrimination
• Psychological effects of obesity
Weight Discrimination
Weight Discrimination
Obesity and Weight Control
The Physiology of Obesity
• Fat Cells
We store energy in fat cells, which become larger & more
numerous if we are obese, and smaller (but still more
numerous) if we then lose weight.
Obesity and Weight Control
The Physiology of Obesity
• Set point
• Metabolism
– Once we become fat, we
require less food to maintain
our weight
– Fat tissue has a lower
metabolic rate
– Overweight person’s weight
drops below previous set
point, hunger ↑ and
metabolism ↓
– Body adapts to starvation by
burning off fewer calories
Obesity and Weight Control
The Physiology of Obesity
• The genetic factor
• The food and activity
factor
–Sleep loss
–Social influence
–Food consumption and
activity level
Obesity and Weight Control
Losing Weight
• Realistic and moderate goals
• Success stories
• Attitudinal changes
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Definition Slide
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Definition
Slides
Motivation
= a need or desire that energizes and directs
behavior.
Instinct
= a complex behavior that is rigidly
patterned throughout a species and is
unlearned.
Drive-reduction Theory
= the idea that a physiological need creates
an aroused tension state (a drive) that
motivates an organism to satisfy the need.
Homeostasis
= a tendency to maintain a balanced or
constant internal state; the regulation of
any aspect of body chemistry, such as
blood glucose, around a particular level.
Incentive
= a positive or negative environment
stimulus that motivates behavior
Hierarchy of Needs
= Maslow’s pyramid of human needs,
beginning at the base with physiological
needs that must first be satisfied before
higher-level safety needs and then
psychological needs become active.
Glucose
= the form of sugar that circulates in the
blood and provides the major source of
energy for body tissues. When its level is
low, we feel hunger.
Set Point
= the point at which an individual’s “weight
thermostat” is supposedly set. When the
body falls below this weight, an increase in
hunger and a lowered metabolic rate may
act to restore the lost weight.
Basal Metabolic Rate
= the body’s resting rate of energy
expenditure.
Anorexia Nervosa
= an eating disorder in which a person
(usually an adolescent female) diets and
becomes significantly (15 percent or more)
underweight, yet, still feeling fat, continues
to starve.
Bulimia Nervosa
= an eating disorder characterized by
episodes of overeating, usually highcalorie foods, followed by vomiting,
laxative use, fasting, or excessive
exercise.
Binge-eating Disorder
= significant binge-eating episodes, followed
by distress, disgust, or guilt, but without
the compensatory purging, fasting, or
excessive exercise that marks bulimia
nervosa.
Sexual Response Cycle
= the four stages of sexual responding
described by Masters and Johnson –
excitement, plateau, orgasm, and
resolution.
Refractory Period
= a resting period after orgasm, during which
a man cannot achieve another orgasm.
Estrogens
= sex hormones, such as estradiol, secreted
in greater amount by females than males
and contributing to female sex
characteristics. In nonhuman female
mammals, estrogen levels peak during
ovulation, promoting sexual receptivity.
Testosterone
= the most important of the male sex
hormones. Both males and females have
it, but the additional testosterone in males
stimulates the growth of the male sex
organs in the fetus and the development of
the male sex characteristics during
puberty.
Sexual Orientation
= an enduring sexual attraction toward
members of either one’s own sex
(homosexual orientation) or the other sex
(heterosexual orientation).