1. Hunger

2. Do Now
Identify correlations between hunger and other ideas/feelings/motivations

3. Hunger Drive
Hypothalamus
Two areas of the hypothalamus, the lateral and ventromedial areas, play a central role in the hunger drive
Keywords: hypothalamus, lateral area, ventromedial area

4. Lateral Area Hypothalamus
Electrical lesions to tract of axons connecting brainstem, hypothalamus and basal ganglia cause a loss of all goal-directed behavior
Stimulation causes drives in response to available incentives
However, chemical lesions to specific cell bodies reduce hunger drive, but do not abolish it - most other drives appear normal
What does this suggest?
Hypothalamus
Keywords: lateral area

5. Ventromedial Area Lesions alter digestive and metabolic processes
Food is converted into fat rather than energy molecules, causing animal to eat much more than normal and gain weight
Hypothalamus
Keywords: ventromedial area

6. Hunger Drive
Other stimuli that act on the brain to increase or decrease hunger include
satiety signals from the stomach
signals indicating the amount of food molecules in the blood
leptin, a hormone indicating the amount of fat in the body
the appetizer effect
Keywords: leptin, appetizer effect

7. Homeostasis Homeostatis and negative feedback governs hunger
Homeostasis: maintaining state: Thermostat
Need sufficient calories
Activation based on anticipation
Why hungry?
Nutrients: basic components of structural integrity (proteins and amino acids stored)
Calories: energy for metabolic processes (glucose, glycogen and fat)

8. Hungry Hungry Hormones
Hormone systems work as feedback loop to turn on/off food seeking or digesting behavior
Insulin: Motivate to seek food when low
Glucose in system leads to insulin release and tells body to stop seeking food
High: about to eat or eating
Cues (sight/smell) elevate glucose
Converts glucose to glycogen for storage
Leptin: released by fat when enough NRG is present (safety valve)
Injection: eat less
Mutated mice receive no negative feedback = overweight
Increasing leptin does not solve obesity as it decreases hunger only up to a certain level
PYY: released form intestines when food is present
Systematic injection: stop eating
Lower presence of PYY in blood for obese people than thin. Thin people show a significant increase in PYY after eating compared to obese people.
Neuropeptide Y: digestive behavior
Produced by hypothalamus
Leptin suppress NPY

9. Research on Weight Regulation and Dieting
No consistent personality trait differences found between obese and non-obese people (e.g., willpower, anxiety)
Dieters and obese are more likely to eat in response to stress than non-dieters
Family environment of little importance in determining body weight - genetics plays a large role
Number of fat-storage cells is a major determinant of body weight
Settling point (set point) - cluster of genetic and environmental factors cause a person’s weight to settle within a given range

10. Research on Weight Regulation and Dieting
Fat cells are determined by genetics and food intake
They increase with weight gain, but merely shrink with weight loss - may stimulate hunger
Weight loss causes a decline in basal metabolism
Fat cells
Normal
diet
High-fat
Return to
normal diet
Keywords: basal metabolism, fat cells

11. Peripheral Cues for Eating (and Stopping)
Full vs. empty stomach
Nutrient level of stomach contents
Glucose levels
Sensory-specific satiety
Can feel satiated on one type of food but then there is renewed interest in a different type of food
All of these factors cause signals in specific area of brain (Stellar’s Dual-Center Hypothesis):
Lateral Hypothalamus (LH) - Hunger Center (“on switch”)
Ventromedial Hypothalamus (VMH) -Satiety Center (“off switch”)

12. Nisbett (1968) - External hypothesis
Subjects arrive hungry
IV-weight of subject (overweight vs. normal)
IV-quantity of visible food (1 vs. 3 sandwiches)
Task: Fill out questionnaires
DV-number of sandwiches consumed
Hypothesis: If overweight people more sensitive to external cues, sight of more food should lead obese to eat more, whereas normal weight people will eat same amount regardless of how much in sight

13. Results Interaction Effect
Quantity of visible food had no effect on the eating behavior of normal weight subjects but for overweight it did. Overweight subjects ate more when more food was visible

14. Psychology and Dieting
Rapid loss of weight means rapid return
Shifting to eating healthier food is more effective than eating less
Apply sensory-specific satiety to each a variety of different healthy foods
Eat meals slowly as it takes 15 minutes for Leptin and PYY to start reaching the brain
Find activities for exercise that you are internally motivated to perform