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Human Motivation Chapter 3 Hunger and Eating. Why do we eat? Biological perspective: zSource of energy zRebuild cells and manufacture various hormones,

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Presentation on theme: "Human Motivation Chapter 3 Hunger and Eating. Why do we eat? Biological perspective: zSource of energy zRebuild cells and manufacture various hormones,"— Presentation transcript:

1 Human Motivation Chapter 3 Hunger and Eating

2 Why do we eat? Biological perspective: zSource of energy zRebuild cells and manufacture various hormones, chemicals, and enzymes zRemove toxins that are often a by-product of eating various foods (Example: antioxidants) Social and psychological perspective: zTo socialize zTo celebrate zForm friendships, reaffirm relationships and commitments o

3 How Do Humans Avoid Toxins? Biological Component: zSmell and taste- first line of defense zGagging, spitting, and vomiting response- second line of defense yThese two defenses are especially prominent in pregnant women, especially in the first trimester when the developing fetus is most at risk. Learned Component: zNatural tendency to avoid new foods zNew foods are sampled in small amounts- toxic foods might only make us sick and through simple conditioning we learn to avoid them in the future zFood preferences are largely learned- taste governs preferences. Cognitive Component: zWide variety of warnings draw attention to danger of certain chemicals zMore and more toxins are getting into the food chain- monitoring these toxins is becoming more and more important zMany toxins that exist in small amounts in food tend to build up in the body over time- researchers suggest eating more antioxidants as a defense

4 Food Selection Carbohydrates: (starches and sugars), broken down into glucose, fructose, and galactose; source of immediate energy- excess glucose can be stored in the liver and muscles. ySpecialized cells of the brain prefer glucose. The body will manufacture glucose from protein (from the body’s muscles) should there be an insufficient supply. Fats: (meats, milk products, seeds/grains), broken down into fatty acids; source of immediate energy or stored under the skin as a reserve; can be made from excess glucose; contains twice as many calories as carbs. Proteins: (meats, beans, nuts, seeds), broken down into amino acids; may be turned into glucose, glycogen, or converted to fat depending on needs; used in body for growth, repair, and energy. Balanced diet = 50-60% carbs, 10-20% fats, 10-20% proteins

5 Humans Evolved as Meat Eaters 1.Extremely difficult for humans to get all essential nutrients from exclusively vegetarian diet. 2.Human body cannot produce vitamins A and B12 (among others that come from meat products)- essential for survival. 3.Amino acids contain components necessary for cell repair and brain functioning. 4.Human gut is dominated by small intestine- site where proteins are broken down. 5.Fossil evidence of ancestor’s teeth. 6.Two million year old bones with cut marks.

6 Food Selection Biological Component: zTaste plays important role in what we should eat and avoid. zUnlearned taste preferences: sweet and fatty. ySweet foods are less toxic and good caloric source. yFats contain number of essential ingredients and contain twice as many calories as carbs. Learned Component: zSeen by the different eating preferences of different ethnic groups. zHuman would learn to eat foods that were available. zLearn to avoid foods that produce aversive state. Cognitive Component: zModern society has come to rely more on our ability to think and reason about what we should/should not eat dependent on extensive scientific research.

7 Hunger Versus Eating Hunger: a biological need yBiological state is linked to chemicals in the body such as insulin and cholecystokin that are released during digestion. yInsulin is released in the body to regulate glucose levels in the body during digestion. Insulin helps glucose from the blood into the cells of the body. xHyperglycemia- glucose levels too high (failure to produce enough insulin- diabetes) xHypoglycemia- too much insulin, glucose levels remain low- stimulating hunger, and more glucose is converted to fat (one of the main culprit of obesity) Eating: many psychological reasons for eating yHabit (Example: because it is lunchtime) yPleasant sensory experience (taste, texture, smell) yOthers are eating

8 The Question of Overweight and Obesity Biological Component: zSubstantial heritability for obesity zEnergy expenditure: BMR, physical activity, SDA yBMR (basal metabolic rate)- amount of energy we use in relation to body size yPhysical activity- 1/3 of our energy ySDA (specific dynamic action) increase in energy following ingestion of food zLesions in the hypothalamus have been linked to overeating zSet-point theory: hypothalamus sets our weight zPositive-incentive theory: eating stops in the presence of palatable food when the positive-incentive value decreases yWe tend to eat more when food tastes good and when there is a variety of food available.

9 The Question of Overweight and Obesity Learned Component: zChild’s weight tends to be more highly correlated with the mother’s weight than the father’s (if purely genetic, correlations equal) zResemblance in weight of siblings decreases in later life. Cognitive Component: zStudy found people lower in self-restraint ate significantly more than people high in self-restraint when a depressed state was induced. zOverweight people are more depressed than normal-weight people- depression is not the cause of being overweight.

10 Theories of Overweight and Obesity Internal-external theory of hunger and eating: some people eat in response to external cues (sight, smell, time of day), whereas other people depend on internal cues (stomach contractions, glucose/fat levels). yNonobese people tend to respond to internal cues, obese people tend to respond to more external cues. ySensory cues of taste/smell are sufficient to stimulate release of insulin in externals- which may stimulate hunger.

11 Theories of Overweight and Obesity The boundary theory of hunger, eating, obesity: two separate mechanisms control hunger and eating- one for hunger, one for satiety. yVary person to person; restrained eaters have lower hunger, higher satiety boundaries than normal eaters. yRestrained eaters (typical dieters)- often feel hungry, think a lot about food, are readily tempted by sight/smell, and consciously attempt to control impulse to eat. xWhen they fail to restrain eating, may become disinhibited to rely on satiety boundary which is higher than nondieter. xStress tends to increase food consumption. yUnrestrained eaters- do not feel persistent hunger, nor think about or are attempted so readily by food, do not try to control food intake and do not feel guilty when they overeat.

12 Difficulties Confronting Dieters Biological Component: zHumans have developed food mechanisms: yto deal with lack of food: decelerates metabolism (anabolism) yto store food. yto prevent buildup of excessive fats: accelerates metabolism (catabolism) Learned Component: zIdeal body enshrined in current cultural norms is lean. zBehavior modification- learn new patterns of eating that will lead to immediate weight loss and help maintain new weight. Cognitive Component: zFailure to self-regulate- failure to control attention in food intake.

13 Food Sharing and Eating as a Social Event Biological Component: zEvolutionary analysis of hunters and gatherers: needed to share what each other had. Learned Component: zMeat spoils quickly- surplus shared first with family and then larger community. zSharing food meant part of a larger family that might come to your assistance during times of trouble. zFood to create/cement alliances and relationships. Cognitive Component: zSharing as expressions of instinctive altruism/empathy. zFood creates basic sense of well-being, trust. zFood creates sense of indebtedness.


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