1. Module 30
Hunger
Josef F. Steufer/Getty Images

2. Hunger The Physiology of Hunger
30-1: WHAT PHYSIOLOGICAL FACTORS PRODUCE HUNGER?
Monitoring stomach contractions
Using this procedure, Washburn showed that stomach contractions (transmitted by the stomach balloon) accompany our feelings of hunger (indicated by a key press). (From Cannon, 1929.)

3. Hunger The Physiology of Hunger Body Chemistry and the Brain
Glucose
Is form of sugar that circulates in the blood and provides the major source of energy for body tissues.
Triggers feeling of hunger when at low levels.
Set Point
Is the point at which the body’s “weight thermostat” is supposedly set.
When the body falls below this weight, increased hunger and a lowered metabolic rate may combine to restore the lost weight.
Basal Metabolic Rate
The body’s resting rate of energy expenditure.

4. Hunger The Physiology of Hunger: Body Chemistry and the Brain
Arcuate nucleus: Neural arc in the hypothalamus that secretes appetite-suppressing hormones.
Ghrelin: A hunger-arousing hormone secreted by the empty stomach.
The hypothalamus (colored orange) performs various body maintenance functions, including control of hunger. Blood vessels supply the hypothalamus, enabling it to respond to our current blood chemistry as well as to incoming neural information about the body’s state.

5. Hunger The Physiology of Hunger Body Chemistry and the Brain
The appetite hormones, in addition to ghrelin :
Insulin: Hormone secreted by pancreas; controls blood glucose
Leptin: Protein hormone secreted by fat cells; when abundant, causes brain to increase metabolism and decrease hunger
Orexin: Hunger-triggering hormone secreted by hypothalamus
PYY: Digestive tract hormone; sends “I’m not hungry” signals to the brain

6. Hunger The Psychology of Hunger Taste Preferences: Biology and Culture
30-2: WHAT CULTURAL AND SITUATIONAL FACTORS INFLUENCE HUNGER?
Body cues and environmental factors influence taste preferences
Genetic and universal preferences for sweet and salty tastes, but conditioning can intensify or alter those preferences
Calming effects of serotonin boost from carbohydrates; when stressed, carbohydrates are extra rewarding

7. Hunger The Psychology of Hunger Taste Preferences: Biology and Culture
Our cultures teaches us that some foods are acceptable but others are not
Among many Japanese: Nattó, a strong-smelling fermented soybean dish
Among many Westerners: “Rotted bodily fluid of ungulate,” a.k.a. cheese
Taste preferences can be adaptive
Spicier food preference in hotter climates; spices that inhibit bacteria growth
Pregnancy-related nausea and food aversion peak at 10 weeks in utero, when the developing embryo is most vulnerable to toxins

8. An Acquired Taste
People everywhere learn to enjoy the fatty, bitter, or spicy foods common in their culture. For these Alaska Natives (left), but not for most other North Americans, whale blubber is a tasty treat. For many Peruvians (right), roasted guinea pig is similarly delicious.

9. Hunger The Psychology of Hunger Situational Influences on Eating
Five situational influences you may have noticed but underestimated:
Arousing appetite: Study showed doubled snacking when watching an intense action movie
Friends and food: Presence of others amplifies natural behavior tendencies (social facilitation)
Serving size is significant: Quantity of consumed food is influenced by size of serving, dinnerware
Selections stimulate: Food variety promotes eating
Nudging nutrition: New practices, such as a school lunch tray making fruits and vegetables more prominent, may improve eating habits

10. Hunger Obesity and Weight Control
30-3: WHAT FACTORS PREDISPOSE SOME PEOPLE TO BECOME AND REMAIN OBESE?
Obesity has been associated with:
Lower psychological well-being, especially among women
Increased depression
60 percent more bullying suffered by obese 6- to 9-year-olds
Physical health risks

11. Hunger Obesity and Weight Control The Physiology of Obesity
A worldwide study of 188 countries revealed:
Proportion of overweight adults increased from 29 to 37 percent among men, and 30 to 38 percent among women
No reduced obesity rate in ANY country in over 33 years
Wide variations by nation
In 2010, no U.S. state had obesity rate less than 20 percent
Extreme obesity carries wide range of health risks

12. Hunger Obesity and Weight Control The Physiology of Obesity
Set Point and Metabolism
Point at which your “weight thermostat” is supposedly set. When your body falls below this weight, increased hunger and a lowered metabolic rate may combine to restore lost weight.
Basal metabolic rate, the body’s resting rate of energy output, differs among individuals, meaning that two people of the same height, age, and activity level can maintain the same weight, even if one eats much less than the other.

13. Hunger Obesity and Weight Control The Physiology of Obesity
The Genetic Factor
People’s weights resemble those of their biological parents
Identical twins have closely similar weights, even when raised apart
The Food and Activity Factors
Sleep loss contributes to fall in leptin levels and rise in ghrelin
Social influence seen in correlation among friends’ weights
Increased food consumption and lower activity levels are seen worldwide
Genes mostly determine why one person today is heavier than another. Environment mostly determines why people today are heavier than their counterparts of 50 years ago.

14. Hunger Obesity and Weight Control The Physiology of Obesity
Past and projected overweight rates, by the Organization for Economic Cooperation and Development

15. Hunger Obesity and Weight Control The Physiology of Obesity
Waist management tips for those wishing to lose weight:
Begin only if you feel motivated and self-disciplined.
Exercise and get enough sleep.
Minimize exposure to tempting food cues.
Limit variety and eat healthy foods.
Reduce portion sizes.
Don’t starve all day and eat one big meal at night.
Beware of the binge.
Before eating with others, decide how much you want to eat.
Remember, most people occasionally lapse.
Connect to a support group.