Understanding Hunger: Physiology, Psychology, and Obesity

1. Unit 8 Motivation, Emotion, and Stress

2. Unit 8 Day 1 –The Basis of Motivation (Module 37) Day 2 –Hunger and Sex (Modules 38 & 39) Day 3 –The Need to Belong (Module 40) and Week 1 Vocabulary Quiz Day 4 –Theories of Emotion and Detection (Modules 41 & 42) Day 5 –Stress and Unit 8 Review (Modules 43 & 44) Day 6 –CUA 8!

3. Module 38:Hunger Motivation

4. Physiology of hunger • Washburn study • Balloon study which indicated that stomach contractions (“rumbles”) are linked to pangs of hunger

5. Hunger Physiology: Biochemistry • Dependent on glucose(the sugar the body uses to power cellular processes); lower glucose = more hunger feelings • Managed by insulin (hormone secreted by pancreas that manages glucose levels) • These feelings are managed by the hypothalamus in the following ways • Lateral hypothalamus gives one the desire to eat (a Large Hunger) • Ventromedial hypothalamus gives the feeling of “fullness” (a Very Minute Hunger) • Orexin is secreted by the hypothalamus and controls feelings of hunger

6. Hunger Physiology: Biochemistry • Appetite hormones: • Orexin– mentioned before, controls hunger • Ghrelin– secreted by stomach when empty (I’m Hungry) • Leptin–secreted by fat cells; more of it means brain stops feeling hungry • PYY– in intestines, sends “not hungry” signals to brain • Combined with brain activity, this means your body tends to revolve around a natural set point, weight influenced by our genetics • Humans differ in basal metabolic rate, or how much energy is needed for the body at rest

7. Hunger Psychology: Taste Preferences • Genetic: humans prefer sweet and salty things • ALL humans are neophobic– a fear of eating new or unfamiliar things • Why? • Humans also have adaptive tastes– cultures near water eat a lot more fish, cultures in plains eat more grain

8. Hunger Psychology: The Situation • Do you overeat when surrounded by others? • Almost certainly yes! Being around others results in social facilitation, or a tendency to overdo our natural behaviors. • Does it matter that food serving sizes are different in different countries? • Hilariously yes! When offered larger or supersized portions, humans tend to eat them! • Does the variety of food matter? • Yep! Like all of the others, humans eat more when offered a greater variety of food (which is why you overeat at the buffet line). These behaviors are adaptive, to consume more food in a time of scarcity.

9. Obesity • Bodies store fat for good reasons. It’s the ideal form of long-term energy storage, and so our ancestors intentionally sought out sweets and salts to up their stored energy. • In the modern world, where these sweets, proteins, and salts are abundant, what is likely to happen? • Simply put, our genetics have not caught up with our culturaland social evolutions. We live in large cities, drive cars more than we walk (there’s a relationship between how good a subway system is and how fat a city’s residents are), and have access to ALL the food we could buy.

10. Obesity Factors • Set point and metabolic rate– we require less food to maintain fat than to gain it, so dieting isn’t always a good way to lose weight. • Genetic influences– our genes influence everything fro what we like to eat, to how much we eat, to how much we move. Identical twins weigh similar even when raised apart, and your weight is likely to be much more similar to your parents than your friends. • Environmental factors– sleep loss in developed countries (Japan, western Europe, the US) is directly tied to weight gain; additionally, social influence of friends – when one of your friends becomes obese, you too are more likely to become obese