Chapter
8
Energy Balance, Body
Composition, and
Weight Management
• by
• Norman D. Sossong, MD, PhD
• for NSCC:
• NTR150 – Spring 2008
Energy Balance
• Energy balance = the balance in the body
between the amount of energy consumed and
expended
• Energy intake = the caloric or energy content of
food provided by the sources of dietary energy:
carbohydrates (4 kcal/g), fats (9 kcal/g), proteins
(4 kcal/g), and alcohol (7 kcal/g)
• Energy output = the use of calories or energy for
basic body functions, physical activity, and
processing of consumed foods
Energy Balance
• Energy equilibrium = a balance of energy intake
and output that results in little or no change in
weight over time
• Positive energy balance = energy intake exceeds
energy expenditure, resulting in an increase in
body energy stores and weight gain
• Negative energy balance = energy intake is lower
than energy expenditure, resulting in a depletion
of body stores and weight loss
Energy In
• Regulation of intake
• Hunger
• Prompts eating;
physiological desire
• Satiation
• Signals to stop eating
• Satiety
• Lack of hunger
• Appetite
• Psychological desire
Energy In: Regulatory Factors
Energy Out: Fuel Uses
• Major components of energy expenditure
• Resting energy expenditure (REE)
• = Basal energy expenditure (BEE)
• Energy for basic body functions
• Affected by body size, composition, age, gender
• Physical activity
• Highly variable
• Affected by body size, fitness level,
type of activity
• Thermic effect of food (TEF)
• Energy to digest, absorb,
metabolize food
Energy Expenditure at Rest
Constitutes 60-75% of total energy expenditure
Measured as: Basal Metabolic Rate (BMR)
= resting metabolic rate (RMR)
Conditions:
Lying at rest
Just awoke from normal sleep
10-12 hours since last meal
No physical activity in the past
12-18 hours
Note: technically the RMR only requires a
3 to 4 hour waiting period after food or
exercise to do the test
Result: the RMR is slightly higher than
the BMR
Factors that Affect Basal
Metabolic Rate (BMR)
Lean body mass
= the body mass (other than
fat)
= muscles and organ tissue
Generally, lean body mass
has more metabolism than
fat; hence it contributes
more to the BMR
Factors that Affect Basal
Metabolic Rate (BMR)
Muscle & organ mass
Liver
Brain
Muscles (resting)
Heart
Kidney
The rest
29%
19%
18%
10%
7%
17%
100%
Factors that Affect Basal
Metabolic Rate (BMR)
Age  2-3%  per decade
 Lean body mass
 Body fat
 Organ function
Keeping physically active
Slows loss of lean body mass
Slows gain of fat
→ preservation of BMR
Factors that Affect Basal
Metabolic Rate (BMR)
Gender: BMR of ♀ < ♂
♀ (female):
smaller
less lean body mass
Menstrual cycle influences:
Low point:
a week before ovulation
High point:
Just before menstruation starts
Factors that Affect Basal
Metabolic Rate (BMR)
• Sleep
• 10% ↓ in BMR
• ↑ lean body mass → ↑ BMR
• (growth spurts, e.g. infancy &
adolescence)
• Hormones
• Thyroid
• Norepinephrine
• Physical stress
Factors that Affect Basal
Metabolic Rate (BMR)
• Fever
• Environmental temperature
• Cold
• Hot
• Mild ↑
• Much ↑
• Starvation
• Genetics
Energy Used in
Various Activities
15-30% of BMR
Energy Used to Process Food
= Thermic Effect of Food (TEF) = 10%
Peaks about 1 hour after eating
Usually gone within 5 hours of eating
Energy
Balance
Estimating Energy Expenditure
• EER: Estimated Energy Requirement
• Predicts total energy expenditure (TEE)
• Equations for males and females
• Factors for age, weight, height, physical activity
• Males:
• EER = 662 – 9.53 x Age (yrs) + PA x [15.91 x Wt (kg) +
539.6 x Ht (m)]
• PA = 1.0 Sedentary
• 1.12 Low active
• 1.25 Active
• 1.48 Very active
Estimating Energy Expenditure
• EER: Estimated Energy Requirement
• Predicts total energy expenditure (TEE)
• Equations for males and females
• Factors for age, weight, height, physical activity
• Females:
• EER = 354 – 6.91 x Age (yrs) + PA x [9.36 x Wt (kg) +
726 x Ht (m)]
• PA = 1.0 Sedentary
• 1.12 Low active
• 1.27 Active
• 1.45 Very active
Body Composition:
Understanding Fatness and Weight
• Assessing body weight
• Height-weight tables
• Body mass index (BMI)
• Weight (kg)  height2 (m)
• Assessing body fatness
• Body fat distribution
• Waist circumference
BMI vs Mortality
Waist Circumference
• If BMI = 25 – 34.9 kg/m2
• Then waist circumference
•
> 40 inches in men
•
or
•
> 35 inches in women
• is a sign of increased health risk
When Energy Balance Goes Awry
• What are the health risks associated with being
overweight?
Risks of Being Overweight
When Energy Balance Goes Awry
• Early theories of weight regulation
• Fat cell theory
• Set point theory
• Influences on weight gain and obesity
•
•
•
•
•
•
Heredity and genetic factors
Sociocultural influences
Age and lifestyle factors
Gender and ethnicity
Socioeconomic factors
Psychological factors
Sociocultural
Influences on
Obesity
Gender Biases
Regarding Body Shape
Weight Management
• Perception of weight
• Setting realistic goals
• Weight management lifestyle
• Diet and eating habits
•
•
•
•
Reduce total calories
Reduce fat calories
Increase complex carbohydrates
Improve eating habits
• Increase physical activity
• Stress management
• Self-acceptance
Weight Management
• Weight management approaches
• Self-help books and manuals
• Watch for signs of a fad diet
•
•
•
•
•
Self-help groups
Commercial programs
Professional counselors
Prescription drugs
OTC drugs and dietary supplements
Weight Management
• Weight
management
approaches
• Surgery
Underweight
• Definition
• BMI < 18.5 kg/m2
• Causes
• Illness
• Eating disorders
• Metabolic factors
• Weight-gain strategies
• Small, frequent meals
• Fluids between meals
• High-calorie foods and beverages