Hunger and Thirst

1. Hunger and Thirst

2. Essential Task Describe classic research findings in specific motivation systems (e.g., eating, sex, social)

3. Thirst • Biology of Thirst • Monitor the level of fluids inside the cells • When levels drop thirst drive is activated • Another system monitors level of fluids outside the cells causing less blood to flow to the kidneys • This in turn causes the activation of the thirst drive • Environmental cues

4. The Biology of Hunger Stomach contractions (pangs) send signals to the brain making us aware of our hunger.

5. Stomachs Removed Tsang (1938) removed rat stomachs, connected the esophagus to the small intestines, and the rats still felt hungry (and ate food).

6. Glucose: C6H12O6 The glucose level in blood is maintained by your pancreas. Insulin decreases glucose in the blood, when the level gets too low, we feel hungry. Glucose Molecule

7. Glucose & 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. Rat Hypothalamus

8. Hypothalamic Centers • The lateral hypothalamus (LH) brings on hunger (when stimulated lab animals ate!). • Destroy the LH, and the animal has no interest in eating. • The reduction of blood glucose stimulates orexin in the LH, which leads one to eat

9. Hypothalamic Centers • The ventromedial hypothalamus (VMH) depresses hunger (satiety) • Destroy the VMH, and the animal eats excessively. Richard Howard

10. Leptin • Fat cells in our body produce leptin • Hypothalamus monitors these levels • High levels of leptin signal the brain to reduce appetite or increase the rate at which fat is burned. • Leptin deficiency can cause obesity

11. The Psychology of Hunger • Environmental cues can trigger the biological responses (increased insulin production) • Memory plays an important role in hunger. Due to difficulties with retention, amnesia patients eat frequently if given food (Rodin et al., 1998). • Emotional attachment? • Conditioning

12. Taste Preference: Biology or Culture? Body chemistry and environmental factors influence not only how much or when we feel hunger but what we feel hungry for! Richard Olsenius/ Black Star Victor Englebert

13. Hot Cultures like Hot Spices Countries with hot climates use more bacteria-inhibiting spices in meat dishes.

14. Social Expectations Screen cap of a Google image search for “magazine”

15. Social Expectations Screen cap of a Google image search for “runway model”

17. Twenty years ago, the average fashion model weighed 8% less than the average woman. Today, she weighs 23%. • A decade ago, plus-size models averaged between size 12 and size 18. Today, the majority of plus-size models an agency boards are between size 6 and size 14

18. Anne Becker • Becker oversaw a 1995-98 study that measured the effect of television on cultural norms. (Television was only catching on in Fiji in 1995. A decade before, even electricity was rare.) • The results were startling. In 1995, without television, girls in Fiji appeared to be free of the eating disorders common in the West. But by 1998, after just a few years of sexy soap operas and seductive commercials, 15 percent of adolescent girls reported they at least once had purged to lose weight. High scores on eating disorder inventories double. • “I want their body,” said one girl of the Western shows she watched. “I want their size.” • By the glow of television, young girls in Fiji “got the idea they could resculpt their lives,” said Becker — but they also began to “think of themselves as poor and fat.” • Television brought with it “a social storm” of many dimensions, she said. For one, it dislocated traditional clans. Becker showed a picture of the chief’s family in their living room. To one side was a television, and on the other was a treadmill.

19. Diet Industry • 108 million people on diets • 85% of them are female • They will spend $20 billion a year • 3% - success rate of the diet industry. John LaRosa of MarketData; National Weight Control Registry; American Society for Metabolic and Bariatric Surgery;

21. Set-Point Theory • According to the set-point theory, there is a control system built into every person dictating how much fat he or she should carry – a kind of thermostat for body fat. • Some individuals have a high setting, others have a low one. • According to this theory, body fat percentage and bodyweight are matters of internal controls that are set differently in different people.

22. How to change the set point • Dieting does nothing • Dieting research demonstrates that the body has more than one way to defend its fat stores. • Long-term caloric deprivation, in a way that is not clear, acts as a signal for the body to turn down its metabolic rate. • The body reacts to stringent dieting as though famine has set in. Within a day or two after semi-starvation begins, the metabolic machinery shifts to a cautious regimen designed to conserve the calories it already has on board. Because of this innate biological response, dieting becomes progressively less effective, • A plateau is reached at which further weight loss seems all but impossible.

23. Messing with Set-Point • Studies show that a person’s weight at the set point is optimal for efficient activity and a stable, optimistic mood. • When the set point is driven too low, depression and lethargy may set in as a way of slowing the person down and reducing the number of calories expended.

24. How to change the set point • The ideal approach to weight control would be a safe method that lowers or raises the set point rather than simply resisting it. • So far no one knows for sure how to change the set point, but some theories exist. • regular exercise is the most promising as a sustained increase in physical activity seems to lower the setting

25. Summary

38. Fashion Show? • Nutritionist measures the model’s body's muscle mass, fat ratio and levels of water retention. • He prescribes protein shakes, vitamins and supplements to keep their energy levels up during this 4 month training period. • Models drink a gallon of water a day. • For nine days before the show they will drink only protein shakes - "no solids". The concoctions include powdered egg. • Two days before the show they will abstain from the gallon of water a day, and "just drink normally". • 12 hours before the show they will stop drinking entirely.