Download Hunger Motivation

Hunger Motivation
Human beings get hungry and need to eat, do so, and then get full, which is the point at which they cannot eat anymore (satiety).
Researchers have investigated which signals from the body and brain cause a person to become hungry, as well as which signals indicate satiety.
WWII Hunger Research
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Read the article about the Minnesota Starvation Experiment about Ancel
Keys and his research group. Answer the questions in your notes.
Hunger Motivation
Washburn and Cannon led some of the early research in hunger. Hunger Motivation
Stomach contractions (pangs) send signals to the brain making us aware of our hunger. When our stomach expands we feel full.
But, research has shown that hunger persists without stomach pangs: Tsang (1938) removed rat stomachs, connected the esophagus to the small intestines, and the rats still felt hungry (and ate food).
The same holds true for people who have had their stomachs removed for cancer treatment. Also, people who have had their stomachs filled by surgical balloons had “full” stomachs but still did not feel satiated.
Body Chemistry & the Brain
Levels of glucose in the blood are monitored by receptors (neurons) in the stomach, liver, and intestines. They send signals to the hypothalamus in the brain.
* Glucose is the form of sugar that circulates in the blood and
provides the major source of energy for the body tissues.
When its levels are low, we feel hungry.
The Appetite Hormones
Blood vessels supply the hypothalamus, enabling it to respond to our current blood chemistry as well as to incoming neural information about the body’s state. One of its tasks is monitoring levels of appetite hormones.
Hormone
Location
Activity
Insulin
Pancreas
Control blood glucose
Ghrelin
Empty stomach
“I’m hungry” signals
Orexin
Hypothalamus
Hunger‐triggering
Leptin (protein hormone)
Fat cells
When abundant, causes brain to increase metabolism and decrease hunger
PYY
Digestive tract
“I’m not hungry” signal
Hypothalamic Centers
The lateral hypothalamus (LH) brings on hunger. Destroy the LH, and an animal has no interest in eating. The ventromedial hypothalamus (VMH) depresses hunger (makes you feel full). Destroy the VMH, and an animal eats excessively.
Set Point
The interaction of appetite hormones and brain activity suggest that the body has some sort of “weight thermostat”.
When the body falls below the set point—or the point at which an individual’s “weight thermostat” is supposedly set—an increase in hunger and a lowered metabolic rate may act to restore the lost weight. This set point is influenced in part by heredity.
Limits of Set Point
It doesn’t address slow, sustained changes in body weight that can alter a person’s set point.
It doesn’t address overeating and weight gain when we have unlimited access to a wide variety of tasty foods.
It doesn’t explain why psychological factors influence hunger.
Many prefer the term “settling point or set range”.
The Psychology of Hunger
Memory plays an important role in hunger. Due to difficulties with retention, amnesia patients eat frequently if given food (Rozin et al., 1998).
This suggests that part of knowing when to eat is our memory of our last meal. Taste Preference: Biology or Culture?
Body chemistry and environmental factors influence not only when we feel hunger but what we feel hungry for!
Whale blubber!
Roasted ants!
The Ecology of Eating
When given a
large serving
utensils or a
large
bowl/plate,
we take more
food.
We eat more when
eating with others.
When offered a
supersized portion,
we put away more
calories.
Obesity
Obesity is a disorder characterized by being excessively overweight. Obesity increases the risk for health issues like cardiovascular diseases, diabetes, hypertension, arthritis, and back problems. In women, there is a increased risk of late‐life cognitive decline.
http://www.cyberdiet.com
Body Mass Index (BMI)
A BMI of 30 or more = obese.
Obesity in children increases their risk of diabetes, high blood pressure, heart disease, gallstones, arthritis, and certain types of cancer, thus shortening their life‐expectancy. In addition, obese children are much more likely to suffer bullying.
2010 Data
Obesity Rates Around the World, 2010
Physiology of Obesity
Fat Cells: There are 30‐40 billion fat cells in the body. These cells can increase in size (2‐3 times their normal size) and number (75 billion) in an obese individual (Sjöstrum, 1980).
The Genetic Factor
Studies reveal that body weight has a genetic basis:
• Identical twins have closely similar weights, even when reared apart. • Given an obese parent, boys are 3x more likely, and girls 6x more likely to be obese than those with normal‐weight parents.
• Adoptive siblings’ body weights are uncorrelated; people’s weights resemble those of their biological parents and siblings.
Social Effects of Obesity
When female job applicants were made to look overweight, subjects were less willing to hire them.
Activity
Lack of exercise is a major contributor to obesity.
Just watching TV for two hours resulted in a 23% increase of weight when other factors were controlled (Hu & others, 2003).
Food Consumption
Over the past 40 years, average weight gain has increased. Health professionals are pleading with US citizens to limit their food intake.
Eating Disorders
Anorexia Nervosa: A condition in which a normal‐
weight person (usually an adolescent woman) continuously loses weight but still feels overweight. They remain obsessed with losing weight, and sometimes exercise excessively.
Usually adolescents and 9
times out of 10 females.
1930s
2010
Eating Disorders
Bulimia Nervosa: A binge‐purge disorder characterized by episodes of overeating, usually high‐calorie foods, followed by vomiting, using laxatives, fasting, or excessive exercise. Depression and anxiety follow binges. Weight fluctuations as usually within or above normal ranges (easier to hide)
Changes in body size throughout history…
Venus of Willendorf: c. 22,000‐21,000 BCE
The Arrival of Marie deʹ Medici at Marseilles, by Peter Paul Rubens 1622‐26
The Bathers, by Pierre Auguste Renoir 1887
1950s sex symbol Marilyn Monroe was a size 10
Modern‐day fashion model vs. Holocaust victim
The Media & Body Image:
Dove’s The Evolution of Beauty
Dove’s Campaign for Real Beauty
The goal of the
Operation Beautiful website
is to end negative self-talk
or “Fat Talk.”
We will study anorexia and bulimia more in Module 69 while studying other abnormal behavior.
Social Motivation
The Need to Belong
“[Man] is a social animal,” (Aristotle).
Separation from others increases our need to belong.
20th Century Fox/ Dreamworks/ The Kobal Collection
“Cast Away,” Tom Hanks, suffers
from social starvation.
Belongingness (Affiliation Need)
1.
2.
3.
4.
Wanting to Belong: The need to belong colors our thinking and emotions.
Social Acceptance: A sense of belonging with others increases our self‐esteem. Social segregation decreases it.
Maintaining Relationships: We resist breaking social bonds, even bad ones.
Ostracism: Social exclusion leads to demoralization, depression, and at times nasty behavior.