energy balance and weight management

• Homeostatic mechanisms include the release of hormones, such as insulin and glucagon, which regulate blood sugar levels.
• Energy balance


  Relationship between energy consumed and energy expended
• Shift in energy balance

  1. Energy consumed = Energy expended - Neutral energy balance

  2. Energy consumed > Energy expended - Positive energy balance

  3. Energy consumed < Energy expended - Negative energy balance
• Measuring energy in


  • Food records
  • Food recalls
  • Feedings
  • Bomb calorimeter
• Measuring energy out


  • Physical activities (30-50%)
  • Basal metabolism (50-60%)
  • Thermic effect of food (minor)
• Basal metabolism


  • About two-thirds of energy expended in a day
  • Metabolic activities
  • All basic processes of life
• Basal metabolic rate (BMR)


  Variations due to weight, lean tissue
• Resting metabolic rate (RMR)


  Variations due to weight, lean tissue
• Factors affecting BMR


  • Weight
  • Lean tissue
  • Age
• Equations to estimate BMR/RMR

  • Harris-Benedict equation
  • Mifflin equation
• Physical activity


  • Voluntary movement of skeletal muscles
  • Most variable component of energy expenditure
  • Depends on muscle mass, body weight, frequency, intensity, and duration
• Thermic effect of food


  • 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
• Adaptive thermogenesis


  • Adapt to dramatically changing circumstances
  • Extra work done by body
  • Amount expended is extremely variable
  • Not included in energy requirement calculations
• Estimating energy requirements


  • Gender
  • BMR
  • Growth
  • Age
  • Physical activity
  • Body composition & body size
• Estimate energy requirement (EER)

  1. Equations for men and women over 19 years

  2. Factors: age, weight, height, physical activity level
• Healthy body weight


  • Not appearance based
  • Depends on amount and location of body fat, body weight, current health status
• Body weight vs body fat

  • Real issue is how much body fat a person has
  • Bodyweight includes fat, bone, muscle, water
• Healthy body fat percentage

  • Men: 12-20%
  • Women: 20-30%
• Body fat distribution


  • Visceral fat (central obesity)
  • Subcutaneous fat (peripheral obesity)
• Waist circumference


  • Indicator of fat distribution & central obesity
  • Women: greater than 35 inches
  • Men: greater than 40 inches
• Body mass index (BMI)

  • Relative weight for height
  • BMI = weight (kg) / height (m)^2
  • Health-related classifications
• BMI is not a measure of body composition and has variations
• Hunger


  • Physiological response to nerve signals and chemical messengers
  • Influenced by hypothalamus
• Satiation


  • Helps control the size of a meal
  • Protein is the most satiating
• Satiety


  • Determines the frequency of meals
  • Fat produces strong satiety signals
• Hunger-satiety-fullness scale


  • Fullness
  • Satiety/Neutral
  • Hunger
• Common eating disorders


  • Anorexia nervosa
  • Bulimia nervosa
  • Binge eating disorder
• Anorexia nervosa


  • Distorted body image
  • Malnutrition impacts brain function and judgment
  • Protein-energy malnutrition similar to marasmus
  • High mortality rate among psychiatric disorders
• Bulimia nervosa


  • Distinct and more prevalent than anorexia
  • Secretive nature
  • Treatment focuses on discontinuing purging and restrictive diet habits
• Binge-eating disorder


  • Periodic binging without purging
  • Contrast with bulimia nervosa
• Female athlete triad


  • Disordered eating
  • Amenorrhea
  • Osteoporosis and stress fractures
• Other dangerous practices of athletes

  • Muscle dysmorphia
  • Food deprivation and dehydration practices
• Society plays a central role in eating disorders, more prevalent as wealth increases and food becomes plentiful