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PS102 Study Guide - Eating Disorder, Brown Adipose Tissue, Libido

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Eileen Wood

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Chapter 12: Motivation
Motivation: an inferred process within a person or animal that causes movement either
toward a goal or away from an unpleasant situation
Intrinsic: the pursuit of an activity for its own sake
Extrinsic: the pursuit of an activity for external rewards (e.g. money or fame)
Motives to Eat
The Biology of Weight
Genetic Influences on Weight and Body Shape
Set point: the genetically influenced weight range for an individual; it is maintained by
biological mechanisms that regulate food intake, fat reserves and metabolism
Basal metabolism rate: rate at which the body burns calories for energy
Everyone has fixed number of fat cells
Obese people have twice the number of fat cells & are bigger
High heritability of weight, body fat & amount of brown fat (fat that burns calories) a
person has weight is gained in the same places
Leptin (hormone) can affect how much a person eats because it affects the hypothalamus in
telling the body when it should eat if reserves are too low
It plays its most crucial role early in life by altering the brain chemistry that
influences how much a person later eats
It helps regulate body weight by strengthening neural circuits in the hypothalamus
that reduce appetite and by weakening circuits that stimulate it during a critical
period in infancy, the point is set
The Overweight Debate
People are become increasingly obese reasons for this have little to do with the
obesity gene, but more diet
Obesity epidemic is in fact fat people getting fatter and thin people staying the same
Exercise is a major influence on weight it boosts metabolic rate even in people who
are genetically susceptible to obesity

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Environmental Influences on Weight
1. Increased abundance of fast food and processed food… that are inexpensive, readily
available, and high in sugar, starch, fat and carbohydrates as humans, we have a
tendency to store calories in the form of fat to be prepared in case of starvation
2. The widespread consumption of high-sugar, high-calorie soft drinks: we don’t have a
mechanism that would compensate for fluid intake by lowering food intake
3. The sharp decline in exercise & other expenditures of energy… because of remote
controls, a preference for sedentary activities & the speed and convenience of driving
rather than walking/biking
4. The increased portion sizes of food and drink.
5. The abundance of highly varied foods: diets that restrict a person to only some foods
are successful at first, but as food becomes more varied, people eat more and gain
more weight (e.g. people will eat more M&Ms when they are in a bowl containing 10
colours than the same number of candies containing only 7 colours.
Other influences: package sizes, plate sizes (bigger = eat more), cues for how much has
been eaten (e.g. buffets taking dirty plates away), kitchen & table layouts, distraction (e.g. TV
& friends)
Culture & the Ideal Body
While people of all ethnicities and social classes have been getting fatter, the cultural
ideal for women in the united states, Canada and Europe has been getting thinner
Voluptuous, big-breasted women are associated with a motherly image that’s why
that body type was more desired in times where women would take the “stay-at-
home-mom” job
Now, with women entering the work force, the same figure is seen as soft, lazy, weak
& therefore women have tried to look more boyish & muscular to avoid being
perceived as soft, feminine and dumb
Evolution has designed women to store fat, which is essential for the onset of
menstruation, pregnancy & nursing, and, after menopause, for the production of
The Body as a Battleground: Eating Disorders
Many women are caught in a battle between their biology and their culture

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Eating disorders: an irrational fear of being fat
Bulimia: an eating disorder characterized by episodes of excessive eating (bingeing) followed
by forced vomiting or use of laxatives (purging)
Anorexia [nervosa]: fear of being fat, a distorted body image, radically reduced consumption
of food & emaciation can die of heart or kidney failure or complications of osteoporosis
Can be influenced by depression, anxiety, perfectionism, low self-esteem, a distorted
body image, drug use & perceived pressure from peers to lose weight, & culture
factors such as the image of the “ideal thin body”
Other eating disorders: binge-eating disorder (just eating A LOT); chewing food & then
spitting it out; others are normal weight but take no joy in eating because they worry
obsessively about gaining weight; some develop phobias of a certain type of food
All of these disorders involve an unhealthy attitude toward food, weight & the body
Motives to Love
The Biology of Love
Passionate “romantic” love: whirlwind of intense emotions and sexual passion – crushes,
infatuations, “love at first sight”, in early stages of love affairs may burn out quickly or
evolve into companionate love
Olfactory cues in a potential partner’s smell that can turn you on or off
Physical cues in the pp’s voice, shape & how similar their face is to yours
Dopamine jolts of reward
Arousal & excitement provided by adrenaline
Key hormones that turn this into companionate love
Companionate love: affection & trust
Love has an evolutionary purpose: to preserve the species share common neural
mechanisms as pair-bonding between a child and its mother
Hormone oxytocin: plays crucial role in the attachment-caregiving system, influencing
feelings & expressions of love, caring & trust between mothers & babies and
between friends and lovers (e.g. when partners were given oxytocin, they showed
more non-verbal cues of love)
Endorphins: chemical substances in the nervous system that are similar in structure and
action to opiates; involved in pain reduction, pleasure & memory
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