Transcript Chapter 3 - Hunger and Eating

Human Motivation
Chapter 3
Hunger and Eating
Why do we eat?
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Biological perspective:
Source of energy
Rebuild cells and manufacture various hormones,
chemicals, and enzymes
Remove toxins that are often a by-product of eating
various foods (Example: antioxidants)
Social and psychological perspective:
To socialize
To celebrate
Form friendships, reaffirm relationships and
commitments
How Do Humans Avoid Toxins?
Biological Component:
 Smell and taste- first line of defense
 Gagging, spitting, and vomiting response- second line of defense
 These two defenses are especially prominent in pregnant women, especially in the
first trimester when the developing fetus is most at risk.
Learned Component:
 Natural tendency to avoid new foods
 New foods are sampled in small amounts- toxic foods might only make us
sick and through simple conditioning we learn to avoid them in the future
 Food preferences are largely learned- taste governs preferences.
Cognitive Component:
 Wide variety of warnings draw attention to danger of certain chemicals
 More and more toxins are getting into the food chain- monitoring these toxins
is becoming more and more important
 Many toxins that exist in small amounts in food tend to build up in the body
over time- researchers suggest eating more antioxidants as a defense
Food Selection
Carbohydrates: (starches and sugars), broken down into glucose,
fructose, and galactose; source of immediate energy- excess
glucose can be stored in the liver and muscles.
Specialized cells of the brain prefer glucose. The body will manufacture
glucose from protein (from the body’s muscles) should there be an
insufficient supply.
Fats: (meats, milk products, seeds/grains), broken down into fatty
acids; source of immediate energy or stored under the skin as a
reserve; can be made from excess glucose; contains twice as
many calories as carbs.
Proteins: (meats, beans, nuts, seeds), broken down into amino
acids; may be turned into glucose, glycogen, or converted to fat
depending on needs; used in body for growth, repair, and energy.
Balanced diet = 50-60% carbs, 10-20% fats, 10-20% proteins
Humans Evolved as Meat Eaters
1. Extremely difficult for humans to get all essential
nutrients from exclusively vegetarian diet.
2. Human body cannot produce vitamins A and B12
(among others that come from meat products)essential for survival.
3. Amino acids contain components necessary for cell
repair and brain functioning.
4. Human gut is dominated by small intestine- site
where proteins are broken down.
5. Fossil evidence of ancestor’s teeth.
6. Two million year old bones with cut marks.
Food Selection
Biological Component:
 Taste plays important role in what we should eat and avoid.
 Unlearned taste preferences: sweet and fatty.
 Sweet foods are less toxic and good caloric source.
 Fats contain number of essential ingredients and contain twice as many
calories as carbs.
Learned Component:
 Seen by the different eating preferences of different ethnic groups.
 Human would learn to eat foods that were available.
 Learn to avoid foods that produce aversive state.
Cognitive Component:
 Modern society has come to rely more on our ability to think and reason
about what we should/should not eat dependent on extensive scientific
research.
Hunger Versus Eating
Hunger: a biological need
Biological state is linked to chemicals in the body such as
insulin and cholecystokin that are released during digestion.
Insulin is released in the body to regulate glucose levels in the
body during digestion. Insulin helps glucose from the blood
into the cells of the body.
Hyperglycemia- glucose levels too high (failure to produce enough
insulin- diabetes)
Hypoglycemia- too much insulin, glucose levels remain lowstimulating hunger, and more glucose is converted to fat (one of the
main culprit of obesity)
Eating: many psychological reasons for eating
Habit (Example: because it is lunchtime)
Pleasant sensory experience (taste, texture, smell)
Others are eating
The Question of
Overweight and Obesity
Biological Component:
 Substantial heritability for obesity
 Energy expenditure: BMR, physical activity, SDA
BMR (basal metabolic rate)- amount of energy we use in relation to
body size
Physical activity- 1/3 of our energy
SDA (specific dynamic action) increase in energy following ingestion
of food
 Lesions in the hypothalamus have been linked to overeating
 Set-point theory: hypothalamus sets our weight
 Positive-incentive theory: eating stops in the presence of
palatable food when the positive-incentive value decreases
We tend to eat more when food tastes good and when there is a variety
of food available.
The Question of
Overweight and Obesity
Learned Component:
 Child’s weight tends to be more highly correlated with the
mother’s weight than the father’s (if purely genetic,
correlations equal)
 Resemblance in weight of siblings decreases in later life.
Cognitive Component:
 Study found people lower in self-restraint ate significantly
more than people high in self-restraint when a depressed state
was induced.
 Overweight people are more depressed than normal-weight
people- depression is not the cause of being overweight.
Theories of
Overweight and Obesity
Internal-external theory of hunger and eating: some people eat in
response to external cues (sight, smell, time of day), whereas other
people depend on internal cues (stomach contractions, glucose/fat
levels).
Nonobese people tend to respond to internal cues, obese people
tend to respond to more external cues.
Sensory cues of taste/smell are sufficient to stimulate release of
insulin in externals- which may stimulate hunger.
Theories of
Overweight and Obesity
The boundary theory of hunger, eating, obesity: two separate
mechanisms control hunger and eating- one for hunger, one
for satiety.
Vary person to person; restrained eaters have lower
hunger, higher satiety boundaries than normal eaters.
Restrained eaters (typical dieters)- often feel hungry, think
a lot about food, are readily tempted by sight/smell, and
consciously attempt to control impulse to eat.
When they fail to restrain eating, may become disinhibited to rely
on satiety boundary which is higher than nondieter.
Stress tends to increase food consumption.
Unrestrained eaters- do not feel persistent hunger, nor
think about or are attempted so readily by food, do not try
to control food intake and do not feel guilty when they
overeat.
Difficulties Confronting Dieters
Biological Component:
 Humans have developed food mechanisms:
to deal with lack of food: decelerates metabolism (anabolism)
to store food.
to prevent buildup of excessive fats: accelerates metabolism
(catabolism)
Learned Component:
 Ideal body enshrined in current cultural norms is lean.
 Behavior modification- learn new patterns of eating that will
lead to immediate weight loss and help maintain new weight.
Cognitive Component:
 Failure to self-regulate- failure to control attention in food
intake.
Food Sharing and Eating
as a Social Event
Biological Component:
 Evolutionary analysis of hunters and gatherers: needed to share
what each other had.
Learned Component:
 Meat spoils quickly- surplus shared first with family and then
larger community.
 Sharing food meant part of a larger family that might come to
your assistance during times of trouble.
 Food to create/cement alliances and relationships.
Cognitive Component:
 Sharing as expressions of instinctive altruism/empathy.
 Food creates basic sense of well-being, trust.
 Food creates sense of indebtedness.