Unit 10: Motivation

1. Unit 10: Motivation Module 35: Hunger

2. Hunger • Ancel Keys (1904-2004) was an American scientist who studied the influence of diet on health. • He conducted The Minnesota Starvation Experiment as WWII was coming to an end! • He used 36 male volunteers and semi-starved them for 24 weeks.

3. Hunger • Results: • The participants lost 25% of their body weight. • They had increased depression, hysteria, and hypochondria. • Some self-mutilated (one subject cut 3 fingers of his hand with an axe). • Sexual interest was reduced as were all other interests, except food. • Could pass Maslow’s first need.

4. Subject swallows balloon, which measures stomach contraction Stomach contractions Subject presses key each time when hungry Hunger pangs 0 1 2 3 4 5 6 7 8 9 10 Time in minutes Hunger • Stomach contractions accompany our feelings of hunger.

5. Hunger • Glucose: the form of sugar that circulates in the blood. • It provides the major source of energy for body tissues. • When its level is low, we feel hunger. • Also stimulating one part of the hypothalamus increases hunger. • Stimulating a different part decreases hunger.

6. Hunger • Orexin: Hunger-triggering hormone. • Ghrelin: Hunger-arousing hormone secreted by an empty stomach. • Gastric bypass surgery seals off part of the stomach resulting in less Ghrelin. • Leptin: Hunger-dampening chemical secreted by fat cells. • PYY: a digestive hormone that suppresses appetite.

7. Hunger • Set Point: the point at which an individual’s “weight thermostat” is supposedly set. • When the body falls below this weight, an increase in hunger. • A lowered metabolic rate may act to restore the lost weight. • Basal Metabolic Rate: Body’s rate of energy expenditure.

8. Hunger • Researchers have doubts about a set point, but instead prefer a settling point. • Settling Point: the level at which a person’s weight settles in response to caloric intake and expenditure.

9. Psychology of Hunger • As time passes since we last ate, we expect to eat again and get hungry. • Carbohydrates boost levels of serotonin, which calms us. • Culture and biology affects the foods we crave. • We avoid unfamiliar foods (neophobia), which protected our ancestors from potentially toxic foods.

10. Psychology of Hunger • 2/3 of Americans are considered overweight. • 1/3 of those overweight are obese. • Body mass index (BMI): a way of measuring obesity. • Obesity causes a multitude of health issues.

12. Eating Disorders • Anorexia Nervosa: a normal weight person diets and becomes significantly (over 15%) underweight, yet still feels fat and continues to starve. • 95% of sufferers are female. • Most are between the ages of 18-30. • 30% of persons diagnosed with anorexia nervosa die.

13. Eating Disorders • Bulimia Nervosa: disorder characterized by episodes of overeating, followed by vomiting, fasting, or excessive exercise. • Eat up to 20,000 calories and then starve or purge (vomit). • Average victim is a young female of average weight. • Takes physical and psychological toll

14. Women’s Body Images Thinnest Fattest Women’s ideal Women’s current body image What women believed men preferred What men actually preferred