Lesson 2 – Hunger Motivation
Hunger Motivation
Hunger seems simple…. You feel hungry when you do not eat… cars need gas and you need food
Hunger: general state of wanting to eat
Satiety (se-TY-a-tee): condition when you no longer want to eat
Biological Basis (signals) of Hunger Motivation
1. Growling stomach:
feel hunger pains when your stomach is empty … and
if you over eat the increased pressure from within the stomach can reduce appetite
But…
people who have lost their appetite due to illness still get hungry if they do not eat
Stomach cues affect eating BUT ARE NOT a major role in the normal control of eating.
Stomach cues operate mainly when you are VERY hungry or VERY full
2. Signals from the Blood
Blood sugar
Experiment – Rats who were deprived of food were injected with the blood of other rats who had just eaten. When offered food, the injected rats ate little or nothing.
What sent the satiety signal????
Recent research has shown that the Brain monitors blood content for the presence of
Nutrients absorbed into blood stream from stomach: glucose, fatty acids, and amino acids
Glucose: main form of sugar used by body cells. IF LEVEL IS LOW… WE FEEL HUNGER
Decades ago researchers found that when level of glucose drops eating increases sharply.
Recently…. Found if glucose levels rise, the pancreas releases insulin, a hormone that most body cells need in order to use the glucose they receive.
and
Hormones released into the blood in response to those nutrients (cholecystokinin, insulin, and leptin) whose presence communicates hunger or satiety.
Insulin: secreted by pancreas controls blood glucose
Leptin: protein secreted by fat calls; if abundant causes brain to increase metabolism and decrease hunger. Declining leptin = hunger and weight gain Increase leptin in animals leads to reduced intake of food and weight loss (SENSORS are in HYPOTHALAUS)
3. Signals from the Brain
Psych Sim with fat rat
Hypothalamus: play roles in the regulation of hunger and eating by monitoring and controlling body chemistry (ration of glucose and insulin, etc.)
Makes us feel hungry when we need to eat
Experiment: electric stimulation of animals in different parts of the hypothalamus act in opposition to control hunger
- Lateral Hypothalamus - makes you eat
LATEral …“IT’S LATE… TIME TO EAT”
electro stimulation of this part of hypothalamus causes animal to eat
Destruction of this causes the end of hunger and animal will starve to death
2. Ventromedial Hypothalamus - makes you not eat
Electro stimulation of this part of hypothalamus causes animal to NOT EAT
Destruction of this causes the animal to eat and eat and gain more and more weight unless food is taken away
Paraventricular nucleus of the hypothalamus is also implicated in consumption cessation.
Do the two regions of the Hypothalamus interact to maintain some homeostatic level or set point?
Too simplistic probably
3.Set Point Hypothalamus may be involved in the homeostatic maintenance of set point.
Set point theory describes how the hypothalamus might decide what impulse to send. Theory being that the hypothalamus wants to set a certain optimum body weight
When we drop below set point the hypothalamus tells us to eat and lowers metabolic rate (how quickly our body uses energy)
When we reach the optimum weight the hypothalamus tells us to stop eating and raises basal metabolic rate to burn excess food
Basal Metabolic Rate: the body’s resting state of energy expenditure
Minimum amount of energy needed to maintain vital functions of the body while awake but at rest.
Measured in calories expended per kilogram of body weight or per square meter of body surface per hour
Possible factor in overeating and obesity: if you have a high set point it would be difficult at best to change.
Individual’s set point could be related to genetic disposition … obesity does run in families (NO GENE FOR THIS HAS BEEN FOUND)… could also be nurture
Possible… chronic feeding in infancy could set a high set point because excess food intake increases size and number of fat cells in the body. Extra fat cells are there for life (unless liposuction)
NOT ALL PSYCHOLOGISTS believe in set point theory… some say weight control is more about learning and cognition than with they hypothalamus
This theory is too simplistic.
4. Certain neurotransmitters also may selectively motivate eating of different kinds of foods.
Psychological Factors in Hunger Motivation:
Nonbiological factors can override the brain’s regulatory processes.
Flavor of food
Appetite
Social rules and cultural traditions
1. Mood effects eating…
Cravings … comfort food
If you are feeling tense or depressed what do you crave???
Starchy carbohydrate laden foods? These increase serotonin which does have calming effects.
In high school… loved chocolate would go for a bag of chocolate chips … Yum
What do you crave when stressed?
Specific hungers, the desire for certain foods at certain times, may reflect the biological need for a nutrient found in those foods.
2. Culture and taste (sweet and salty tastes are universal but others are conditioned)
Social cues tell people what and how much are appropriate to eat in certain social situations. Culturally-based delicacies, portion sizes, and speed of consumption are all factors in how much we will eat.
a. Raised on highly salted food and you will develop a liking for salty food
b. Bedoins like eating Camel eyes and we would most likely not eat dog, rat or horse (loved elsewhere)
Some northern Europeans put mayo on a lot of items…
Power Point Slide – market in Beijing China: Menu: Seahorse - RMB30, Scorpion - 8, Cicada - 5, Stinky Fish - 3 and Starfish which are not listed.
What do you eat that others might not like?
Evolutionary value of diet for certain culture…. Hot climates use more spices (spicy food) the spices kill bacteria and keep food fresher longer in climates where spoilage is of greater risk.
Japan: eat wasabi with sushi
3. Conditioning
a. Learn to avoid foods that make us sick taste aversions – eat something and you become sick right after … not because of that food but still you may develop an aversion to it (kids are sick a lot so lots of opportunity)
b. sight of food can elicit conditioned responses such as saliva production associated with eating
4. Novel taste avoidance (Evolutionary Beneficial) – Humans (and other animals like rats) have a natural wariness of unfamiliar things including new foods.
A friend has never had lobster and says she never will - avoid it as new …. Not hungry enough
Experiments show … if you try new or novel foods with repeated exposure appreciation and increases and exposure to one new set of foods increases willingness to try others
Summary hunger is BOTH physiological and psychological
External Incentives: How food smells, tastes and how it looks (Not psychological but still affect hunger). Restaurant décor?
Example: I do not prefer to eat basket food
No basket food
If motivated by incentives … you are more likely to eat
Food on TV and in advertising:
Always looks bigger – sprayed with wax to look more appealing
Glue instead of real milk in cereal commercial to look better
Food Stylists
Eating Disorders:
World Health Organization: condition in which BMI is greater than 30
Those with BMI of 25-29.9 are considered overweight.
BMI determined by dividing a person’s weight in kilograms by the square of the person’s height in meters. Kg/m
5’2” and 165 pounds would be considered obese
also person who is 5’10” and 207 pounds
Obesity is a condition of severe overweight that can contribute to diabetes, high blood pressure, and increased risk of heart attack.
Physiological factors that may predispose people to obesity include body type, more and larger fat cells, and a higher set point.
Psychological factors include maladaptive reactions to stress. Recently, many obese individuals have turned to surgery for weight loss. Conditioning: learning behaviors that lead to obesity from parents
Behavioral factors: Inadequate exercise an activity combined with overeating (especially high fat foods prevalent in western cultures) has much to do with obesity …. BUT
Not all inactive individuals that eat high-fat diets become obese and some obese people are as active as lean ones.
Genetic predisposition to obesity?
Why are Americans gaining weight?
The great American feedlot – farmers have known for thousands of years that to fatten up an animal you need to put it in a pen so it cant run around and feed it lots of grains. People are the same
Vast majority get too little exercise.
Average American watches 30 hours of tv yet say they do not have time to exercise
We have a huge abundance of cheap food and a food industry that spends tons of money to get us to eat more!
Set Point and weight loss for obese- Metabolic changes related to weight loss.
When food intake is reduced … process of homeostasis lead to a drop in metabolic rate which saves energy and curbs weight loss
THIS IS EVOLUTIONARY…. Conservation of energy during a famine is adaptive
Obese people try to lose weight, their metabolic rate drops below normal making it possible for them to gain weight even when eating amounts that would maintain weight in others
TRYING TO LOSE A LOT OF WEIGHT FAST will lead to compensatory changes in metabolism
Yo-Yo Diets
95 % of wt lost is regained within a year
Some dieters put on more wt than lost
Famine hypothesis
Fat cells “think” there must be a famine while dieting
Rebound when person stops diet to help body survive the next “famine”
Advise of Experts…
There is no easy route to weight loss
Permanent changes in your lifestyle
Set reasonable goals
Exercise: critical factor in long run
Anorexia Nervosa eating disorder characterized by a preoccupation with food, self-starvation, and dramatic weight loss. LIFE THREATENING
Characterized by behaviors resulting in weight loss below 85% of normal.
About 95% of sufferers are young females.
Despite hunger, refusal to eat.
Causes serious, often irreversible physical damage.
Incidence appears to be increasing.
Causes not clear
Physical causes are unknown
Psychological factors that contribute include a perfectionist personality and an obsession with thinness.
Photo: Anorexia was named in the 1870’s when it began showing up in adolescent girls of wealthy classes.
(1930’s photo on left and modern teen actresses such as Mary-Kate Olson)
Bulimia nervosa Eating disorder is characterized by binging and purging and is usually not life-threatening. The victim may be thin, normal weight, or overweight.
Binging; eating large amounts of food in a short time
Purging: getting rid of food by vomiting, excessive exercise or use of laxatives
Usually not life threatening
But still has consequences.
Dehydration, nutritional problems, intestinal damage, often develop dental problems from acids associated with vomiting, frequent vomiting and insertion of objects to induce vomiting can cause throat damage.
Causes: cultural factors, emotional problems, and possibly malfunctioning biological mechanisms.
Different cultures have very different rates of eating disorder possibly due to emphasis of body weight within a culture. U.S. has one of the hightest rates
Facts about Obesity in America
- From 1994 to 2002 the percentage of overweight adults in the U.S. increased from 55.9 to 65.7%
- From 1994 to 2002 the percentage of obese adults in the U.S. increased 22.9 to 30.6%
- Problem is so widespread that funeral industry now must offer larger than normal coffins and oversized hearses
- Nearly 300,000 deaths in the U.S. alone related to obesity each year it has been described as at least as dangerous as smoking and alcohol abuse
- In the U.S. 35% of normal-weight girls and 12% of underweight girls begin dieting as young as 9 or 10
(Bernstein Text 2006 edition)
International Impact of Obesity – How Does the U.S. Compare?
In barely a decade, the estimated number for obesity in adults worldwide has skyrocketed from 200 million to more than 300 million.
Currently, obesity levels range from below five percent in China, Japan and certain African nations, to over 75 percent in urban Samoa.
Since 1980, obesity rates have risen three-fold or more in some areas of North America, the United Kingdom, Eastern Europe, the Middle East, the Pacific Islands and Australia
At my nieces 8 year old b-day party two of the girls ordered diet coke… REALLY?
Parents putting 5 year olds on diets?
Movie Intro
Talk about 200 lb six year old on Dr. Phil
show video Medical Mysteries
PSYH SIM WITH FAT RAT?
GIVE DIETING HANDOUT – WORKSHEET
WHEN BASIC NEEDS ARE NOT MET,
EXPECT THE FOLLOWING:
#1 You will always be thinking about what is needed: (sleep, water, air, food, warmth)
#2 It is hard to concentrate or think about anything else.
#3 There is a powerful craving to satisfy the need. (tiredness, thirst, hunger, etc.)
#4 Until satisfied, the craving is very uncomfortable. You may become irritable,
and self centered - its hard to think about other's feelings
#5 When the need is finally met, more than a normal amount is needed.
DIETERS CAN EXPECT THE FOLLOWING:
1) A dieter is almost constantly thinking about FOOD.
2) When dieting, it is hard to CONCENTRATE or think about anything else.
3) There is a POWERFUL craving for FOOD, especially fast energy foods like sweets and high fat foods.
4) Not satisfying hunger is very UNCOMFORTABLE. It is not surprising dieters may have LITTLE patience, feel CRABBY and may be thinking most about THEIR OWN needs.
5) A HUGE hunger is felt when a dieter stops dieting. This makes a dieter feel they cannot get enough food. It is normal to expect to rapidly eat a LARGE amount of food when going off a diet – far MORE than a normal amount. Dieters may not know they are full until they feel "STUFFED".
6) The longer and more often a dieter diets, the MORE overeating occurs after the diet. One of the most common causes of overeating is DIETING.
7) After losing weight on a diet, most people REGAIN the weight, plus ADDITIONAL pounds.
8) The more people diet, the harder it is to tell when they are full and when they are still HUNGRY. They may always FEEL hungry, even if they are not. If they stop dieting long enough, they may get back their normal hunger sensor, but they also may not.