Transcript Would we eat without hunger?

Would we eat without hunger?



Feelings of hunger are not always a product
of our body’s need for nutrition.
Rats who have had their stomachs cut out,
thereby eliminating hunger pangs, still eat.
Humans are the same.
Filling our stomachs on low-calorie food
leads to hunger faster than not completely
filling our stomachs on high-calorie food.
Why we eat




The hypothalamus plays a role in both eating and
feeling full.
Animals and humans automatically regulate their
caloric intake to maintain a stable weight.
When glucose (blood sugar) drops, we feel
hungry.
When stressed, we crave carbs because they help
boost serotonin in the brain.
Experimental starvation (Keys et
al, 1950)



Subjects volunteered to go on a “starvation diet”
(reduce body weight to 75% of previous levels)
under supervision.
In the starvation phase, personality changed:
became apathetic, irritable, aggressive,
uninterested in sex, and obsessed with food.
In the “refeeding” phase, they were still obsessed
with food, and negative outlook continued. Many
never got their optimism and cheerfulness back.
Experimental overeating (Sims)




Prisoners volunteered to put on 20-30 lbs.
After initially gaining weight easily, they had
trouble gaining.
Food became repulsive, and they quickly lost
weight again when they started eating normally.
Normal-weight people have trouble increasing
their weight substantially, and the added weight is
hard to maintain.
Set-point theory




States that our body has a ‘weight thermostat” to
keep our weight stable.
Heredity influences both our body type and our
set point.
If you start losing too much weight, your
metabolism slows down to try to conserve
calories. If you start gaining too much, your
metabolism speeds up to try to burn off calories.
Set point also adjusts our metabolic rate—resting
rate of energy expenditure.
Problems with set-point theory



Why does set point vary from person to
person?
Why are some people’s set points set at
“obese?”
Researchers say there are too many factors
involved in hunger and eating; it’s not as
simple as a set-point.
Positive incentive model




An alternative to set-point theory
States that people are motivated by personal
pleasure (the taste of food), social context (eating
out with others), and biological factors (how
hungry are you?)
Having a variety of food promotes overeating;
supermarket diet for rats increases weight by
269%.
Set-point theory ignores the factors of taste,
learning, and social context in eating.
Obesity—General findings





Overeating is not the sole cause of obesity, but it
is a large factor.
Overweight people tend to eat more than normalweight people do, especially foods high in fat and
calories.
Overweight people tend to be less physically
active than normal-weight people.
Metabolic levels change both with food intake
and energy output. Metabolism is probably
slower in overweight people.
Binge eating is a risk factor for obesity.
Internal-external hypothesis




Schachter (1968)
People often fail to listen to their own internal
cues for eating and pay attention to the external
cues (food taste, smell, & variety).
Some people are more sensitive to external cues
(appealing foods). These people are called
externals.
Study by Rodin & Slochower with girls at
camp—externals gained more weight because
they munched on candy after a full meal
Normal weight vs. obese:
findings



Normal weight people pay more attention to
internal rather than external cues.
Obese people are more likely to eat something
that looks or smells good even when they’re not
hungry.
One study found that obese people eat 7times
more than normal weight people do during exam
time, though they ate the same amounts at other
times.
Restraint theory


When people are trying to lose weight, they
deliberately ignore their internal hunger
cues and try to use cognitive rules to limit
their eating.
Could backfire because denying yourself
food may lead you to binge.
Treating obesity



Losing weight boils down to two things: eat less
and exercise more.
In 2001, 70% of high school girls and more than
30% of boys were dieting.
Several approaches to weight loss: restrict portion
size, restrict types of food you eat, increase
exercise, rely on drastic medical procedures, or
use a combination of the above.
Restricting types of food




Reducing portion size is reasonable and healthy,
but people find it difficult to do.
High-protein, low carb diets can produce rapid
weight loss, but people find it very difficult to
stay on these diets. May be unhealthy as well
(high cholesterol). These diets produce fatigue
and depression after only a few days.
High-carb, low fat diets can be safe and effective.
Limiting yourself to a liquid diet or single food
group is very unwise. They’re nutritional
disasters.
How to succeed when restricting
food groups



Most experts agree that eating a diet high in fiber
from fruits and vegetables is a good strategy.
Instead of going on a “diet,” experts advise a total
lifestyle change. Learn to eat healthier, and
incorporate exercise into your routine
permanently.
Behavior modification programs—gradual weight
loss & maintenance of that loss are emphasized.
Helps you change your thoughts about food and
your eating behavior. Behaviors, not
consequences, are rewarded.
Characteristics of successful
weight loss




Most successful dieters lost weight on their own
without going through a formal weight loss
program.
Obese children who lose weight are more likely
to maintain the weight loss than adults are.
If you’re not overweight, then dieting to lose a
few pounds is not a good strategy. Better to just
try to eat healthy foods.
It’s healthy to gain up to 7 pounds per decade as
you age.
Exercise



Exercise is not effective for spot reduction (e.g.,
toning thighs). You must have aerobic exercise
for this.
Exercise is at least equal to dieting in controlling
weight & much better than dieting in changing
the ratio of fat to muscle tissue.
Wood et al. (1988): Exercisers vs. dieters vs.
controls—runners lost only fat tissue & retained
more lean muscle tissue.
More about exercise



Exercise produces weight loss through changes in
metabolic rate, rather than through burning
calories.
Cutting down by 500 calories a day produces a
pound of weight loss every week (because 3500
calories = 1 lb of body fat).
Moderate physical activity is sufficient to control
weight. 30 minutes of moderate physical activity
every day is needed, and only 25% of Americans
get that.
Exercise dropouts




For cardiovascular health, you need to walk
briskly 3 hours a week (or 6 miles/week) to
reduce your risk of heart attack by 30-40%.
Those most likely to exercise are males, younger
people, having a past history of physical activity,
and attaining higher levels of education/income.
Women cite self-consciousness as a barrier to
exercise.
People who are smokers, in poor health, and very
stressed are less likely to begin an exercise
program and more likely to quit one.
Anorexia nervosa: Diagnostic
criteria


Defined by the DSMIV-R as intentional weight
loss to a point where you lose 15% of normal
weight, or have a BMI of 17.5 or less. Also
included are a fear of being fat, preoccupation
with food or dieting, a distorted body image, and
cessation of menstrual periods for 3 cycles or
more.
Two subgroups: 1) restricting type and 2) bingepurging type (which is different from bulimia)
Demographics of anorexics



Usually young, white women who are outwardly
compliant and high achievers in school
Preoccupied with food, like to cook for others,
insist that others eat their food, but eat almost
nothing themselves.
Tend to be ambitious, perfectionistic, unhappy
with their bodies, and come from high-achieving,
overprotective families.
When weight loss exceeds 25%


People start acting like Keys’ starving subjects.
They “lose their personalities” to the disease.
Person constantly feels chilled, grows a soft
downy covering of body hair, loses scalp hair,
loses interest in sex, and develops an unusually
preoccupation with food. Hostility toward others
then develops as starvation level becomes deadly.
What motivates anorexics to
starve themselves?




Experts view the disease as an attempt by girls to
gain control.
Anorexics are typically troubled girls who feel
incapable of changing their lives.
They see their parents as overdemanding and in
absolute control of their lives, but they are too
compliant to rebel openly.
They enjoy being hungry and see food as the
enemy.
Cognitive-behavioral therapy




An increasingly popular treatment option for
people with anorexia
Goal is to change the cognitive distortions that
accompany body image problems and eating
behavior.
Therapists attack these distortions while
maintaining a warm and accepting attitude toward
patients.
Patients are taught to discard absolutist, “all-ornothing” attitudes about food.
Other approaches





Another, fairly new approach, comes out of
Maudsley Hospital in London.
Involves getting parents involved as part of the
solution instead of part of the problem.
Parents are given absolute control over their
child’s eating—basically allowed to force-feed
the patient.
Success is limited to adolescents.
Prozac is helpful for preventing relapse.
Diagnostic criteria for bulimia
nervosa




Recurrent episodes of binge eating, a sense of
lack of control over eating, and inappropriate,
drastic measures to compensate for binging.
Some bulimics fast or exercise excessively, but
most use self-induced vomiting or laxatives to
maintain weight.
Contrary to anorexics, bulimics want to maintain
a relatively normal weight (some are slightly
overweight) instead of lose weight.
It’s easier to hide bulimia because weight remains
fairly normal.
Characteristics of bulimia





Bulimia patients eat in spurts.
Most are women in their late teens or twenties.
They’re typically older than anorexic patients.
Preoccupied with food, fearful of becoming
overweight, and are depressed and anxious.
Feel depressed and ashamed after binges.
Bulimics often have other psychological
problems, such as impulsivity, drug or alcohol
abuse, sexual promiscuity, suicide attempts, or
shoplifting/stealing.
More characteristics of bulimics



Childhood experiences with sexual abuse,
physical abuse, and posttraumatic stress are
correlates of bulimia.
About ¼ of sex abuse victims turn out to be
bulimic later.
Bulimics show poor coping skills and find
it difficult to deal with stressful events.
Prognosis for bulimics



Bulimics have an advantage over anorexics in
that they understand their own behavior is wrong
and harmful. Anorexics see nothing wrong with
their eating patterns.
Cognitive behavior therapy is very effective for
bulimia and results in 80% reduction in binging.
Antidepressants are not as effective as therapy in
the treatment of bulimia.
Males with eating disorders




It’s very unusual for a male to develop an eating
disorder, but it does happen.
Whereas women who develop the disorders feel
fat, men who develop the disorders usually are
overweight.
Men are often more concerned with muscle
definition and may diet for athletic reasons.
21% of men who develop eating disorders are gay
and diet to please a lover.
The media’s role in eating
disorders


Supermodels are thinner now than ever
before. Reinforcement of dieting or
slimness appears in only 10% as many
male-directed articles and ads as in
women’s.
When women are on magazine covers, it’s
usually a body shot. Men usually get just a
face shot.
Study with 500 University of
Pennsylvania students



Women’s ideal body weight was less than
their current weight.
Women believed men preferred them to
weigh less than what the men actually
preferred.
Men judged their own weight to be
identical to what their ideal weight should
be and what women wanted them to weigh.