Chapter 8: Eating Disorders

Energy Balance

• energy in = energy out

• imbalance causes weight changes (NOT SIMPLY FAT)

• excess energy → stored as fat

  • fat used for energy between meals

rule of thumb:

• 1 pound fat = 3500 kcal (500 kcal per day for a week)

• not totally correct → differs by gender and weight

Energy In: Food Intake Regulations

• appetite → integrated response to sight, smell, thought, or taste of food

  • psychological response initiates/delays eating

• hunger → physiological response to nerve signals and chemical messengers

  • hypothalamus responsible for hunger

  • influenced by absence of nutrients in bloodstream

• satiation → signal to stop eating

  • food enters GI tract → hunger diminishes

• satiety → signal to not start eating again

  • feeling of satiety suppresses hunger so one doesn’t eat again for a while

Energy Out

total energy components:

• basal metabolism → 50-65%

• physical metabolism → 30-50%

• thermic effect of food (digestion) → 10%

Basal Metabolism

• 2/3 of daily energy

metabolic activities:

• all basic life processes

• basal metabolic rate (BMR)

  • slowest during sleep

  • depends on body weight and lean tissue mass

• resting metabolic rate (RMR)

  • slightly higher than BMR

Estimated Energy Requirements (EER)

• gender → women have lower BMR due to less lean body mass

• age → declines during adulthood as lean body mass diminishes

• body composition/size → BMR higher in taller people and people with larger surface area/weight

• physical activity

Mifflin-St. Jeor Equation → (1lbs = 0.454 kg, 1 inch = 2.54 centimeters)

• males → kcal/day = 10(weight in kg) + 6.25(height in cm) - 5(age in years) + 5

• females → kcal/day = 10(weight in kg) + 6.25(height in cm) - 5(age in years) - 161

Total Energy Expenditure (TEE) = EER * Physical Activity (PA)

physical activity factors:

• 1.2 → little to no exercise

• 1.375 → light exercise (1-3/week)

• 1.55 → moderate exercise (3-5/week)

• 1.725 → heavy exercise (6-7/week)

• 1.9 → very heavy exercise (2/day)

Body Composition

• proportions of muscle, bone, fat, and other tissue make up total body weight

  • body weight = fat + lean body mass (including water)

• BMI = weight (kg) / height (m)²

Anorexia Nervosa

• distorted body image

• malnutrition

  • impacts brain function and judgement

  • lethargy, confusion, and delirium

• denial high among anorexics

  • unhealthy weight loss goals

Bulimia Nervose

• more prevalent than anorexia nervosa

• not as physically apparent (BMI)

• recurrent episodes of binge eating

• recurrent inappropriate compensatory behavior to prevent weight gain

  • self-induced vomiting

  • laxative abuse

• negative self-perception → restrictive dieting → binge eating → purging

Female Athlete Triad

• combination of disordered eating, amenorrhea, and osteoporosis

• disordered eating

  • unsuitable weight standards by themselves or coaches

  • perceived to improve performance

• amenorrhea

  • low blood estrogen, infertility, and bone mineral loss

• osteoporosis

  • caused by reduced estrogen

  • increased risk of stress fractures

Treatment of Eating Disorders

• multidisciplinary approach

  • teams of physicians, nurses, psychiatrists, family therapists, and dietitians

  • high mortality rate