Hunger is both physiological and psychological. Motivation of HUNGER Hunger is both physiological and psychological.

Hunger When do we eat? When we are hungry. When are we hungry? When there is no food in our stomach. How do we know when our stomach is empty? Our stomach growls. These are also called hunger pangs.

Biological Basis of Hunger Hunger does NOT come from our stomach. It comes from our… Brain What part of the brain? The Hypothalamus

Body Chemistry Glucose The hormone insulin converts glucose to fat. When glucose levels drop- hunger increases. Increases in insulin increase hunger, increases in glucose decrease hunger.

Glucose: C6H12O6 Insulin and Glucose are two substances in the blood the form of sugar that circulates in the blood provides the major source of energy for body tissues when its level is low, we feel hunger The glucose level in blood is maintained. Insulin decreases glucose in the blood, making us feel hungry. Insulin and Glucose are two substances in the blood that are critical in regulating hunger levels Glucose Molecule

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

The Physiology of Hunger-Washburn Study Stomach contractions (pangs) send signals to the brain making us aware of our hunger. OBJECTIVE 6| Describe the physiological determinants of hunger.

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

How does the hypothalamus work? Two Theories Set Point Hypothalamus acts like a thermostat. We are meant to be in a certain weight range. When we fall below weight our body will increase hunger and decrease energy expenditure (Basic Metabolic Rate). What happens if we go above our set point? Leptin Leptin is a protein produced by bloated fat cells. Hypothalamus senses rises in leptin and will curb eating and increase activity. Can leptin injections help me?

Set-Point Theory Manipulating the lateral and the ventromedial hypothalamus alters the body’s “weight thermostat.” If weight is lost, food intake increases and energy expenditure decreases. If weight is gained, the opposite takes place.

Motivation-Hunger Set Point Basal Metabolic Rate the point at which an individual’s “weight thermostat” is supposedly set when the body falls below this weight, an increase in hunger and a lowered metabolic rate may act to restore the lost weight Basal Metabolic Rate body’s base rate of energy expenditure

Basal Metabolic Rate The rate at which the body uses energy for vital functions while at rest Factors that influence BMR Age Sex Size Genetics Food intake

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

Hypothalamus & Hormones Tissue Response Orexin increase Hypothalamus Increases hunger Ghrelin increase Stomach Insulin increase Pancreas Leptin increase Fat cells Decreases hunger PPY increase Digestive tract The hypothalamus monitors a number of hormones that are related to hunger.

Ventromedial Hypothalamus Lateral Hypothalamus Ventromedial Hypothalamus When stimulated it makes you hungry. When lesioned (destroyed) you will never be hungry again. When stimulated you feel full. When lesioned you will never feel full again.

Psychological Aspects of Hunger Internals versus Externals The Garcia Effect

The Psychology of Hunger Externals: people whose eating is triggered more by the presence of food than internal factors.

Motivation and Behavior— Hunger and Eating Psychological factors: visual cues, cultural conditioning Obesity is common for Pima Indians in U.S., but not for those living in nearby Mexico with traditional diet.

The Psychology of Hunger Memory plays an important role in hunger. Due to difficulties with retention, amnesia patients eat frequently if given food (Rozin et al., 1998). OBJECTIVE 7| Discuss psychological and cultural influences on hunger.

Taste Preferences Food taste better and we chew less when we are hungry (beginning of a meal). Food tastes worse and we chew more when we are not hungry (at the end of the meal). Its weird, the better the food tastes, the less time we leave it in our mouths.

Taste Preference: Biology or Culture? Body chemistry and environmental factors influence not only when we feel hunger but what we feel hungry for!

Culture and Taste

Culture and Hunger

Dog Mice Wine Fried Frog Legs Criadillas- bull testicles.

According to incentive models of hunger, the availability and palatability of food are key factors regulating hunger. An abundance of diverse foods tends to lead to increased eating. p. 380

Cultural Factors Countries with hot climates, in which food historically spoiled more quickly, feature recipes with more bacteria-inhibiting spices India averages nearly 10 spices per meat recipe, Finland 2 spices.

Effects of Culture and Habits on Body Weight Baseline body weight—cluster of genetic and environmental factors that cause a person’s weight to settle within a given range Weight can be affected by factors like diet, exercise, and daily habits (e.g., stairs instead of elevator)

Factors Contributing to Being Overweight Highly palatable food—we eat because it tastes so good Supersize It—food portions are larger than necessary for health Cafeteria Diet Effect—more food and more variety leads us to eat more Snacking—does not cause us to eat less at dinner BMR—changes through the lifespan Sedentary lifestyles

Eating Disorders Anorexia Nervosa An eating disorder in which a normal weight person diets and becomes significantly underweight, yet, still feeling fat, continues to starve.

Eating Disorders: Anorexia Nervosa An anorexic is defined as a person who has stopped eating and is at least 25% underweight. Anorexics have low self-esteem and a distorted body image. They see themselves as being overweight. Every system in the body can be damaged. As the body adjusts to extremely low food intake, it becomes unable to handle nourishment except in very, very small amounts. As with bulimia, most victims are female.

Eating Disorders Bulimia Nervosa An eating disorder characterized by episodes of overeating, usually of high caloric foods, followed by vomiting, laxative use, fasting, or excessive exercise.

Eating Disorders: Bulimia Nervosa Bulimia is characterized by overeating (bingeing) and induced (forced) vomiting. 80-85% of bulimics are female Low self-esteem is a major factor Males lose weight for sport competition Causes irritation to the throat and mouth and future digestive problems Causes erosion to the teeth enamel

Reasons for Eating Disorders Sexual Abuse: Childhood sexual abuse does not cause eating disorders. Family: Younger generations develop eating disorders when raised in families in which weight is an excessive concern. Genetics: Twin studies show that eating disorders are more likely to occur in identical twins rather than fraternal twins.

Obesity A disorder characterized by being excessively overweight. Obesity increases the risk for health issues like cardiovascular diseases, diabetes, hypertension, arthritis, and back problems. http://www.cyberdiet.com

Obesity Severely overweight to the point where it causes health issues. Mostly eating habits but some people are predisposed towards obesity. Click on the pictures to see some case studies on obesity.

The Social Effects of Obesity Obesity stereotypes: slow, lazy, sloppy Obese people are rated as less sincere, less friendly, meaner, and more obnoxious Weight discrimination: obese people made $7000 a year less than equally intelligent comparison Obesity has been associated with lower psychological well-being, and increased depression and anxiety

THE PHYSIOLOGY OF OBESITY Set point & Metabolism Once we become fat, we require less food to maintain our weight than we did to attain it. Why? Because compared with other tissue, fat has a lower metabolic rate. When an overweight person’s body drops below its previous set point, the person’s hunger increases and metabolism decreases. The body adapts to starvation by burning off fewer calories.

THE GENETIC FACTOR The specifics of our genes predispose the size of our jeans  People’s weights resemble those of their biological parents. Identical twins have closely similar weights, even when reared apart.

THE FOOD AND ACTIVITY FACTORS Sleep—people who skimp on sleep are more vulnerable to obesity. Social influence– people are more likely to become obese when a friend became obese. People across the globe are getting fatter. We must change food consumption and activity levels.

LOSING WEIGHT The condition of an obese person’s body reduced to average weight is much like that of a semistarved body. Held under normal set point, the body “thinks” it is starving. Having lost weight, formerly obese people look normal, but their fat cells may be abnormally small, their metabolism slowed, and their minds obsessed with food.

Body Image (Women) Western culture tends to place more emphasis on a thin body image in comparison to other cultures.

Figure 12.7 Levels of analysis for our hunger motivation Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers