Motivation-Hunger AP Psych

Ancel Keys Experiment Fed 36 volunteers just enough to maintain initial weight. Then cut rations in half. Body stabilized at 25% below starting weight Began conserving energy Became food obsessed All efforts were focused toward their next meal Lost interest in any activities not involving food (sex, social activities) Food and hunger has a powerful effect on us. Louis Zamperini would spend 49 days adrift on a raft at sea in the Pacific. He and the other survivor spent their days discussing food.

Physiology of Hunger Our stomachs contract when we feel hungry This is only one source of hunger

Blood Chemistry cause hunger When our blood glucose level drops, signals will be sent from the stomach, intestines, and liver to the brain to trigger hunger The hypothalamus triggers hunger (4 F’s) monitors the body’s appetite hormones Damage to the hypothalamus can create weight difficulties – either too much or little.

The appetite hormones Insulin: Secreted by pancreas; controls blood glucose Leptin: Secreted by fat cells; when abundant, causes brain to increase metabolism and decrease hunger Orexin: Hunger-triggering hormone secreted by hypothalamus. Ghrelin: Secreted by empty stomach; sends out “I’m hungry” signals to the brain; decreases after meals Pyy: Digestive tract hormone; sends “I’m not hungry” signals to the brain.

Set Point & BMR Set point – the point at which an individual’s “weight thermostat” is supposedly set. When the body falls below this weight, a decreased metabolic rate may act to restore the lost weight The theory of the set point is not as widely believed anymore. Basal metabolic rate – the body’s resting rate of energy expenditure Researchers believe people reach a “settling point,” the level at which a person’s weight settles in response to caloric intake and expenditure

Psychological and Cultural Factors Part of being hungry is knowing when our last meal occurred, and what time we normally eat at. Psychological influences on eating behavior are most extreme when the desire to be thin overwhelms normal homeostatic pressures

Taste Preferences Both biology and culture play a role in food preferences. Carbs boost Serotonin levels, creating a calming effect. This leads to the label of comfort foods. Preferences for sweet or salty is genetically based. Some taste preferences are conditioned – an acquired taste

Taste Preferences Cont’d Different cultures enjoy different foods With repeated exposure, taste appreciation for a food typically increases Taste preferences can be adaptive – hotter climates traditionally used more spice to kill bacteria Pregnancy relate nausea and cravings – changing hormone levels affect taste preferences Haggis!!!

Situational Eating People eat more when they are eating with others – explains why we may eat more during the holidays Portion size – Countries that offer servings in smaller sizes are thinner on average

Eating Disorders Anorexia Nervosa – An eating disorder in which a person (most likely an adolescent) diets and becomes significantly (15% or more) underweight, yet still feeling fat continues to starve Bulimia nervosa – an eating disorder characterized by episodes of over eating, usually high calorie foods, followed by vomiting, fasting, laxative use, or excessive exercise Binge-eating disorder – significant binge eating, followed by guilt, without the purge of bulimia

Eating Disorders Cont’d Genetics may influence susceptibility to eating disorders There are cultural factors In India, women rate their shape the closest to their actual shape In Africa, being a little larger means prosperity Generationally, the number of eating disorders have risen as 50% of women say they feel negative about their appearance

Gender Differences Muscle dysmorphic disorder – bigorexia – People with this disorder obsess about being too small and frail and undeveloped. Even if they have good muscle mass, they believe their muscles are inadequate. Men are more likely to be overweight, and women are more likely to perceive themselves as overweight

Media and Body Image Part of the issues with body image in today’s society are what is portrayed “sexy” or “attractive” in the media People begin to idealize media portrayals which leads to dissatisfaction with personal body image If Barbie were real, she would be about 6’ tall, have a 39” bust, 18”waist, 33” hips

Obesity Statistics World Health Organization estimates 1 billion people are overweight 300 Million people are obese (BMI > 30) United States adult obesity = 34% (doubled in last 40 years) – does not include overweight U.S. Child-teen obesity has quadrupled Australia – 54% of pop. Overweight or obese Canada – 49% France – 42 % Weight in LBS. X 703 = BMI Height in Inches squared

BMI Body Mass Index – A calculation of your height and weight gives you your BMI BMI < 25 = Healthy BMI 25 = Overweight BMI > 30 = Obese Obesity leads to greater risk of serious diseases

Social Effects of Obesity Weight discrimination has been proven, sometimes at greater rates than race and gender Obesity has been associated with lower psychological well being more likely to suffer from depression and anxiety

Physiology of Obesity Fat Cells – Body fat is determined by the size and number of fat cells As fat cells grow, they divide and grow, multiplying the number of fat cells. A person can shrink the cells to lose weight, but the number will never decrease

Set Point and Metabolism Fat has a low metabolic rate, so it takes less food energy to maintain fat than to gain it When a person’s weight drops below it’s settling point, the body responds as though it is being starved During starving, metabolism drops to burn fewer calories, and a person feels more hunger For this reason, the amount of food that maintained weight before a diet, will increase weight after the diet ends This makes it difficult to keep weight off once it has been gained and lost

Genetic Factors Studies have shown that people’s weights resemble those of their biological parents Scientists have found many different genes that influence body weight If one has an obese parent, a boy is 3 times more likely, and a girl 6 times more likely to become obese as an adult

Food and Activity Sleep loss makes one more vulnerable to obesity Leptin falls, and ghrelin rises Social Factors – There is a correlation that close friends share similar BMI’s In the modern days, food portion sizes are greater, and with T.V. and the internet, activity is down. This has led to greater rates of obesity. College cafeteria buffets Since 1960, the average adult American has grown 1 inch and gained 23 pounds

Proposed Reforms Establish a fast-food-free zone around schools Slap an extra tax on calorie rich junk food and soft drinks o Denmark has done this Use “unhealthy food tax” revenues to subsidize healthy foods and to finance health-supportive nutritional advertising

Losing Weight Healthy 2/3 of women, and ½ of men say they want to lose weight 1.Begin if you feel motivated and self disciplined 2.Minimize exposure to tempting food cues 3.Boost your metabolism Exercise and 7-8 hours of sleep empties fat cells, builds muscle, and speeds up metabolism

Losing Weight Healthy Cont’d 4. Eat healthy foods Whole grains, fruits, vegetables, and healthy fat such as that found in olive and fish oil 5. Don’t eat just 1 big meal a day This slows metabolism 6. Don’t binge