Eating Weight Chapter 4 Why do We Eat

Eating & Weight Chapter 4

Why do We Eat?

Models l Set Point Model l Genetics Model l l Homeostasis for Weight Fat Stores Decrease, Hunger Induced Weight is Largely Hereditary Positive Incentive Model l l Positive reinforcement: Eating is Pleasurable (taste) Role of biological factors & social context

What do we eat? Gatekeepers 1. Taste 1. 2. 3. 2. Bitter Sweet Sour Smell 1. Bad smelling

What Determines How much We Eat? 1. 2. 3. 4. 5. Individual experience with food Availability of Food Variety of Food Tasty food Social Setting l l Eating alone vs together What time to eat? Culture encouragement Cultural ideal for body weight

Sensory Specific Satiety l Hedonic value l l Role of variety Faster satiation rates with constant diet

Digestive System Peristalsis l Stomach l Small intestine l Large intestine l

Basic Metabolism l Nutrients: ingredients in food that provide energy or sustain our cells and tissues l Divided into macronutrients (carbohydrates, protein, and fat) and micronutrients (vitamins, minerals, etc. )

Basic Metabolism Carbohydrates Proteins Glucose Amino Acids Energy Level Falls Glycogen (liver) Triglycerides (excess fat) Fatty Acids Glycerol

Local Theories l Tells us why do we get hungry & thirsty? Stomach (S) contractions l Cutting vagus nerve (Between S and CNS) l

Central Theories l Role of Brain l Hypothalamus l Sympathetic and parasympathetic l Pituitary gland l Endocrine system l Behavior: feeding, drinking, sexual, aggression, fear l Homeostatic regulation

Regulation of Hunger Blood Sugar Glucoreceptors (Both inhibit & trigger) Eating Short term regulation(when and how much we eat) l Long term regulation (energy stores) l

Regulation of Hunger l Short term regulation (STR; when and how much we eat) l Ventromedial Hypothalamus (VMH; satiety centre) l l When destroyed hyperphagia Lateral Hypothalamus (LH; hunger centre) l When destroyed aphagia and adipsia

Regulation of Hunger l Glucostatic theory of hunger l l Mayer (1955) Glucoreceptors Inconsistent support l l Damaging VMH did not result in obesity LH may be only triggered in extreme stressful situations

Regulation of Hunger l l Peripheral detectors for STR Stomach l l Duodenum (site of glucoreceptors) l l l Ghrelin (hunger signal)and Obestatin (suppressant) CCK (halts eating) Liver (both) Pancreas (beta cells) l l Insulin (helps transport glucose into cells) Amyline (satiation)

Regulation of Hunger l Long term Regulation l l Set-point theory: A Lipostatic Theory of Hunger LH regulates the normal weight l l l Damaging VMH pulls up body’s set point Leptin (lean people have low leptin levels) l l l Damaging LH lowers body’s set point Low levels signal low fat stores and prompts eating Insulin (glucose availability and fat storage) When one diets both Leptin and Insulin goes down and vice versa

Three Types of Eating Disorders l l Anorexia nervosa- Characterized by a pursuit of thinness that leads to selfstarvation Bulimia nervosa- Characterized by a cycle of binging followed by extreme behaviors to prevent weight gain, such as purging.

Eating Disorders l What are eating disorders? l l Controlling body weight Anorexia l DMS-IV-TR l l l l Types? l l l Refuse to maintain body weight Intense fear of gaining weight Disturbance in the way the body is perceived Absence of 3 menstrual cycles Intentional weight loss to a point weighing less than 85% BMI of 17. 5 or less Restricting Purging Who is anorexic? l l l Influence of culture images European American Women receive this diagnosis. 5% to 1% 15 -29 age group

Anorexia Nervosa l Begins with individuals restricting certain foods, not unlike someone who is dieting Restrict high-fat foods first l Food intake becomes severely limited l

More on anorexia nervosa l May exhibit unusual behaviors with regards to food. l Preoccupied with thoughts of food, and may show obsessivecompulsive tendencies related to food l May adopt ritualistic behaviors at mealtime. l May collect recipes or prepare elaborate meals for others.

Neurobiology of Anorexia l Neurobiology l l Serotonin: Low levels l l depression Heredity l l l Cortisol Blood pressure Brain atrophy: Cognitive tasks 5 -10% prevalence rate Twin studies (monozygotic twins) Brain Structures l l Parts of Limbic structure (includes hypothalamus, the amygdala, and the hippocampus) These are involved in motivation, emotion, learning, and memory

Anorexia Nervosa l Treatment l Poor motivation l Resisting suggestions l Force feeding l Cognitive Behavioral Therapy l Attacking irrational beliefs l Building reasonable habits

Eating Disorders l l Bulimia Eating huge quantities of food in an uncontrolled manner (binge) and getting rid of the food by vomiting or using laxatives (purge) Two subtypes l Purging type l l Self-induced vomiting and laxatives as a way to get rid of the extra calories they have taken in Non-purging type l Use a period of fasting and excessive exercise to make up for the binge

Eating Disorders l Bulimia l DSM-IV-TR l l l Who is bulimic? l l Recurrent episodes of binging Sense of lack of control over eating Inappropriate and drastic measures to compensate for the binge Self evaluation is unduly influenced by body shape 4. 1% women 0. 2% men Restricted to western cultures-white upperclass Is it harmful? l l l Large quantities of sweets-Hypoglycemia Vomiting-Electrolyte imbalance Anemia

Bulimia Nervosa l Qualitatively distinct from anorexia l l A binge may or may not be planned l l Characterized by binge eating Marked by a feeling of being out of control The binge generally lasts until the individual is uncomfortably or painfully full

Bulimia Nervosa l Common triggers for Binge eating Behavior l l l Difficulty in handling emotions: Dysphoric Mood Interpersonal Stressors Restrictive dieting: Intense Hunger After A Period Of Intense Dieting Or Fasting Feelings Related To Weight, Body Shape, And Food Are Common Triggers To Binge Eating Loss or separation Uncertain about mood onset

Bulimia Nervosa l Feelings of being ashamed after a binge are common l l Behavior is kept a secret Tend to adhere to a pattern of restricted caloric intake l Usually prefer low-calorie foods during times between binges

More on bulimia nervosa Later age at the onset of the disorder l Are able to maintain a normal weight l Will not seek treatment until they are ready l l Most deal with the burden of hiding their problem for many years, sometimes well into their 30’s

More on bulimia nervosa l Life events l Sexual abuse Hours of darkness l

Theories l Socio Cultural Approach l l Clinical Approach l l Low self esteem psychological health Social Contagion l l Changing body norms Norms will spread to people experiencing distress Serotonin hypotheses l High level of norepinephrine (eating) low level of serotonin (satiety)

Eating Disorders l Bulimia l Treatment l Usually motivated to seek treatment unlike anorexics l Interpersonal psychotherapy l Changes in attitude and food l Cognitive Behavioral Therapy l Prevention

Anorexia vs. Bulimia

Anorexia Diagnostic Criteria Bulimia Anorexia vs. Bulimia 1. There is refusal by the patient to maintain body weight at or above a minimally normal weight for age and height. 2. There is intense fear of gaining weight or becoming fat even though they are underweight. There are recurrent episodes of binge eating. An episode of binge eating is characterized by both of the following: 1. Eating, in a discrete period of time an amount of food that is definitely larger than most people would eat during a similar period of time and under similar circumstances. 2. Sense of lack of control over eating during the episode. Recurrent inappropriate compensatory behavior in order to prevent weight gain, such as self induced vomiting, misuse of laxatives or diuretics, enemas, or other medications; fasting; or excessive exercise Weight Markedly reduced Usually normal Sex Hormones level Low estrogen and testosterone Usually normal Glucose levels Hypoglycemia Usually normal Age Onset Mid adolescence Late adolescence to late adulthood Menstruation (Amenorrhea) Absent usually normal Mortality 5% Very low

Eating Disorders PURGE BINGE Anorexics may or may not Anorexics do not Bulimics do Binge eaters only do not Binge eaters do Anorexics Bulimics Restrictive Type Purge Type Binge-purge Type Non-Purge Type

Some statistics l l l Eating disorders have increased threefold in the last 50 years 10% of the population is afflicted with an eating disorder 90% of the cases are young women and adolescent girls Up to 21% of college women show sub-threshold symptoms 61% of college women show some sort of eating pathology

Psychological factors l Low self-esteem l Feelings of inadequacy or lack of control in life l Depression, anxiety, anger, or loneliness

Interpersonal Factors l Troubled family and personal relationships l Difficulty expressing emotions and feelings l History of being teased or ridiculed based on size or weight l History of physical or sexual abuse

Social Factors l l l Cultural pressures that glorify "thinness" and place value on obtaining the "perfect body" Narrow definitions of beauty that include only women and men of specific body weights and shapes Cultural norms that value people on the basis of physical appearance and not inner qualities and strengths

Overeating and Obesity l What is Obesity? l Skin fold l Water Immersion l Body Mass Index l It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. l It may overestimate body fat in athletes and others who have a muscular build. l It may underestimate body fat in older persons and others who have lost muscle l http: //nhlbisupport. com/bmicalc. htm l Waist circumference l If most of your fat is around your waist rather than at your hips, you’re at a higher risk for heart disease and type 2 diabetes. l This risk goes up with a waist size that is greater than 35 inches for women or greater than 40 inches for men.

Overeating and Obesity l Other methods of estimating body fat and body fat distribution include measurements of l l l Calculation of waist-to-hip circumference ratios, Techniques such as ultrasound, computed tomography, and magnetic resonance imaging (MRI). For assessing someone's likelihood of developing overweight- or obesity-related diseases, the National Heart, Lung, and Blood Institute guidelines recommend looking at two other predictors: l The individual's waist circumference (because abdominal fat is a predictor of risk for obesity-related diseases). l Other risk factors the individual has for diseases and conditions associated with obesity (for example, high blood pressure or physical inactivity).

Overeating and Obesity l Why are some people obese? l Setpoint Model l Genetics l l l Evolution Twin studies Positive incentive l l l Internal thermostat which regulates weight Role of hormones Positive reinforcement Availability of food How unhealthy is obesity? l l l Blood pressure Gall bladder disease Type 2 diabetes

Processed Foods

Other Obesity Explanations l l l Adaptiveness Gone wrong Genetics-More fat cells Obesity as maintain obesity l l Role of habituation l l Eating behavior may occur when caloric intake is not required Obesity as addiction l l l Hyperinsulinmia: Obese people have high insulin that increases fat storage. Dieting: Low metabolic rate makes weight loss difficult Low metabolic rates (burn few calories) Pleasure of eating Lack of control Stress l Chronic stress increased ghrelin levels

Obesity Prevalence http: //www. iaso. org/resources/world-mapobesity/? map=adults

2010 State Obesity Rates State % State % Mississip pi 34. 0 Arkansas 30. 1 South Dakota 27. 3 Rhode Island 25. 5 New Jersey 23. 8 West Virginia 32. 5 Georgia 29. 6 North Dakota 27. 2 Washingt on 25. 5 Vermont 23. 2 Alabama 32. 2 Indiana 29. 6 Maryland 27. 1 New Mexico 25. 1 Montana 23. 0 South Carolina 31. 5 Kansas 29. 4 Nebraska 26. 9 Wyoming 25. 1 Massachu setts 23. 0 Kentucky 31. 3 Ohio 29. 2 Oregon 26. 8 25. 0 Hawaii 22. 7 Texas 31. 0 Pennsylv ania 28. 6 Maine 26. 8 New Hampshir e Minnesot a 24. 8 Connectic ut 22. 5 Louisiana 31. 0 Iowa 28. 4 Florida 26. 6 Alaska 24. 5 Utah 22. 5 Michigan 30. 9 Illinois 28. 2 Idaho 26. 5 Arizona 24. 3 Nevada 22. 4 Tennesse e 30. 8 Delaware 28. 0 Wisconsi n 26. 3 California 24. 0 District of Columbia 22. 2 Oklahom a 30. 4 North Carolina 27. 8 Virginia 26. 0 New York 23. 9 Colorado 21. 0

Dieting l Approaches to losing weight l Food restriction l Low carbohydrate diet l Have high drop out rates l B-Mod l Healthy eating habits l Use of diaries, self-rewards and penalties l Dieters main 60% of weight loss.

Dieting l l Approaches to losing weight l Exercise l Speeds body metabolism l Drastic means l Diet pills, fasting and laxatives l Gastric bypass or gastric banding surgery l Liposuction l Maintenance l Problem of relapse l Keeping ideal weight by fruits, vegetables and whole grain cereals Is dieting a good choice? l Some do not recommend l Some gain benefits

Regulation of Thirst Intra cellular fluid l Extra cellular Fluid l Interstitial fluid l Intravascular fluid l l Dry Mouth

Regulation of Thirst l Intra cellular fluid l l Extra cellular Fluid l l l Osmometric thirst Volumetric thirst Kidney (absorbs 99% of the fluid) Renin l Angiotensin-stimulates adrenal cortex to secrete aldosterone (reabsorption of SODIUM & Water) l l Angiotensin II The ability of kidney to do this is called ADH and VP

Regulation of Thirst l Osmometric thirst l l Volumetric thirst l l Osmosis (equalize concentration of fluids) Osmoreceptors –trigger drinking OVLT controls water intake Hypovolemia-reduction in fluid balance Angiotensin stimulates thirst motivation Non-homeostatic Drinking Inhibitory control of drinking l Inhibitory mechanisms are less developed

Sexual Motivation l Sex Hormones: Organization and Activation l l Mammalian Brain is female unless altered Sexual Dimorphism l Y and X chromosome

Sexual Motivation l l Hypothalmic Regulation Tumors in hypothalamus lead to early sexual development l l Spinal cord damage represses Mating behavior increases activity in the preoptic area

Aggression Motivation l l Limbic system Destruction of parts of limbic system leads to low aggression l l l LH stimulation biting attack VMH stimulation Amygdala inhibits Destroying thalamus inhibits Affective attack-cats hissing high emotionality Quiet biting attack-low emotionality

Types of Aggression l l l l l Predator Aggression Intermale aggression Fear-induced aggression Territorial defense Maternal aggression Instrumental aggression Serotonin suppresses Intermittant explosive disorder HAA & PAG controls aggression