Chapter8

Energy Balance Energy Balance and Body and Body

CompositionComposition

Chapter 8Chapter 8

Energy BalanceEnergy Balance

• Excess energy is stored as fat• Fat is used for energy between meals

• Energy balance: energy in = energy out• A shift in balance causes weight changes

• Not simply fat changes

• 1 pound of fat = 3500 kcalories

Energy In: Food CompositionEnergy In: Food Composition

• Direct measure of food’s energy value• Bomb calorimeter

• Indirect measure of energy released• Oxygen consumed

• kCalorie calculations

Energy In: Food IntakeEnergy In: Food Intake

• Hunger• Physiological response to nerve signals and

chemical messengers• Hypothalamus

• Influences

• Satiation – stop eating• Satiety – not to start eating again

Hunger, Satiation, and SatietyHunger, Satiation, and Satiety


• Overriding hunger and satiety• Stress eating

• External cues• Time of day, availability, sight, taste of food

• Environmental influences• Examples

• Cognitive influences• Disordered eating


• Sustaining satiation and satiety• Nutrient composition

• Protein is most satiating

• Low-energy density

• High-fiber foods

• High-fat foods – strong satiety signals


• The hypothalamus• Control center for eating• Integrates messages

• Energy intake, expenditure, storage

• Gastrointestinal hormones

Energy Out Energy Out

• Thermogenesis • Basal metabolism• Physical activity• Food consumption• Adaptation

Energy Out: Basal MetabolismEnergy Out: Basal Metabolism

• About two-thirds of energy expended in a day

• Metabolic activities• All basic processes of life• Basal metabolic rate (BMR)

• Variations

• Weight

• Lean tissue

• Resting metabolic rate (RMR)

Factors that Affect the BMRFactors that Affect the BMR

Energy Out: Physical ActivityEnergy Out: Physical Activity

• Voluntary movement of skeletal muscles• Most variable component of energy

expenditure• Amount of energy needed

• Muscle mass• Body weight• Activity

• Frequency, intensity, and duration

Energy Out: Thermic Effect of Energy Out: Thermic Effect of FoodFood

• Acceleration of GI tract functioning in response to food presence• Releases heat

• Approximately 10 percent of energy intake• High-protein foods vs. high-fat foods• Meal consumption time frame

Energy Out: Adaptive Energy Out: Adaptive ThermogenesisThermogenesis

• Adapt to dramatically changing circumstances• Examples

• Extra work done by body• Amount expended is extremely variable• Not included in energy requirement

calculations

Components of Energy Expenditure

Estimating Energy Estimating Energy RequirementsRequirements

• Gender• BMR

• Growth• Groups with

adjusted energy requirements

• Age• Changes with age

• Physical activity• Levels of intensity

for each gender

• Body composition & body size• Height

• Weight

Defining Healthy Body WeightDefining Healthy Body Weight

• Ideal• Not appearance based

• Perceived body image and actual body size

• Damaging behaviors

• Subjective• Little in common with health

Tips for Accepting a Healthy Body Weight

Defining Healthy Body WeightDefining Healthy Body Weight

• Body mass index• Relative weight for height

• BMI = weight (kg)

height (m)2

• Health-related classifications• Healthy weight: BMI = 18.5 to 24.9

• Other classifications

• Not a measure of body composition • Variations

BMI and Body ShapesBMI and Body Shapes

Distribution of Body Weights Distribution of Body Weights in US Adultsin US Adults

Body Fat and Its DistributionBody Fat and Its Distribution

• Important information for disease risk• How much of weight is fat?• Where is fat located?

• Ideal amount of body fat depends on person


• Needing less body fat• Some athletes

• Needing more body fat• Example groups

• Fat distribution• Visceral fat

• Central obesity

• Subcutaneous fat

““AppleApple”” and and ““PearPear”” Body Body Shapes ComparedShapes Compared


• Waist circumference • Indicator of fat distribution & central obesity

• Women: greater than 35 inches

• Men: greater than 40 inches

• Waist-to-hip ratio

• Other techniques for body composition• More precise measures

Common Methods Used to Common Methods Used to Assess Body FatAssess Body Fat

Health Risks Associated with Health Risks Associated with Body Weight & Body FatBody Weight & Body Fat

• Body weight and fat distribution correlate with disease risk and life expectancy• Correlations are not causes

• Risks associated with being underweight• Fighting against wasting diseases• Menstrual irregularities and infertility• Osteoporosis and bone fractures

BMI and MortalityBMI and Mortality


• Risks associated with being overweight• Obesity is a designated disease

• Health risks

• More likely to be disabled in later years• Costs

• Money

• Lives

• Yo-yo dieting


• Cardiovascular disease• Elevated blood cholesterol & hypertension• Central obesity

• Diabetes – type II• Central obesity• Weight gains and body weight

• Cancer• Relationship is not fully understood


• Inflammation & metabolic syndrome• Change in body’s metabolism

• Cluster of symptoms

• Fat accumulation• Inflammation

• Elevated blood lipids• Promote inflammation

• Fit and fat versus sedentary and slim

Eating DisordersEating Disorders

Highlight 8Highlight 8

Eating DisordersEating Disorders

• Three disorders• Anorexia nervosa• Bulimia nervosa• Binge eating disorder

• Prevalence of various eating disorders• Causes

• Multiple factors

• Athletes and eating disorders

Female Athlete TriadFemale Athlete Triad

• Disordered eating• Unsuitable weight standards

• Body composition differences

• Risk factors for eating disorders in athletes

• Amenorrhea• Characteristics

• Osteoporosis • Stress fractures

Female Athlete TriadFemale Athlete Triad

Other Dangerous Practices of Other Dangerous Practices of AthletesAthletes

• Muscle dysmorphia• Characteristic behaviors• Similarities to others with distorted body

images

• Food deprivation and dehydration practices• Impair physical performance

• Reduce muscle strength

• Decrease anaerobic power

• Reduce endurance capacity

Tips for Combating Eating Disorders

Anorexia NervosaAnorexia Nervosa

• Distorted body image• Central to diagnosis

• Cannot be self-diagnosed

• Malnutrition• Impacts brain function and judgment• Causes lethargy, confusion, and delirium

• Denial • Levels are high among anorexics


• Need for self-control• Protein-energy malnutrition (PEM)

• Similar to marasmus

• Impact on body• Growth ceases and normal development

falters• Changes in heart size and strength• Other bodily consequences


• Treatment• Multidisciplinary approach

• Food and weight issues

• Relationship issues

• After recovery• Energy intakes and eating behaviors may not

return to normal

• High mortality rate among psychiatric disorders

Bulimia NervosaBulimia Nervosa

• Distinct and more prevalent than anorexia nervosa• True incidence is difficult to establish

• Secretive nature

• Not as physically apparent

• Common background characteristics of bulimics


• Binge-purge cycle• Lack of control• Consume food for emotional comfort

• Cannot stop

• Done in secret

• Purge• Cathartic

• Emetic

• Shame and guilt

The Vicious Cycle of Restrictive The Vicious Cycle of Restrictive Dieting & Binge EatingDieting & Binge Eating

Negative self-perceptions

Purging Restrictive dieting

Binge eating

Stepped Art

Figure 8-H2 p257


• Physical consequences of binge-purge cycle• Subclinical malnutrition

• Effects

• Physical effects• Tooth erosion, red eyes, calloused hands

• Clinical depression and substance abuse rates are high


• Treatment• Discontinuing purging and restrictive diet

habits• Learn to eat three meals a day

• Plus snacks

• Treatment team• Length of recovery

• Overlap between anorexia nervosa and bulimia nervosa

Diet Strategies for Combating Diet Strategies for Combating Bulimia NervosaBulimia Nervosa

Binge-Eating DisorderBinge-Eating Disorder

• Periodic binging• Typically no purging

• Contrast with bulimia nervosa• Compare with bulimia nervosa

• Feelings

• Differences between obese binge eaters and obese people who do not binge

• Behavioral disorder responsive to treatment

Eating Disorders in SocietyEating Disorders in Society

• Society plays central role in eating disorders• Known only in developed nations• More prevalent as wealth increases

• Food becomes plentiful

• Body dissatisfaction• Characteristics of disordered eating

Chapter8

Health & Medicine

Transcript of Chapter8