Module 8

Question 1

Law of Conservation of Energy

Answer 1

• Energy (E) cannot be created or destroyed, but it
can change form. Some forms of energy are:
– Heat energy
– Chemical energy
– Potential energy
• Energy balance occurs when energy consumed
equals energy expenditure

Question 2

Kilojoules (kJ)

Answer 2

• Unit of work
• Amount of work required to move a 1 kg
object 1 meter under the force of gravity

Question 3

Kilocalories (kcal)

Answer 3

• Unit of heat
• Amount of heat (energy) required to raise
the temperature of 1 kg of water 1 °C

Question 4

Calories vs Kcal

Answer 4

• 1000 Calories = 1 kcal
– A calorie is the amount of heat needed to raise
the temperature of 1 g of water by 1 °C

Question 5

Sources of Energy

Answer 5

Energy is consumed 
in the diet as:
– Carbohydrates 
(4 kcal/g)
– Fats (9 kcal/g)
– Proteins (4 
kcal/g)
– Alcohol (7 
kcal/g)

Question 6

Direct Calorimetry

Answer 6

Obtains a direct measurement of the amount of heat generated by the body within a structure large enough to permit moderate amounts of activity.

Question 7

Bomb Calorimeter

Answer 7

– Instrument used to measure 
the energy content of food.
– Chamber surrounded by 
jacket of water
– Dried food is burned in 
chamber
– Released heat raises 
temperature of the water
– Increase in water temperature 
used to calculate the amount 
of Energy in the food

Question 8

Heat is generated by metabolic

reactions that

Answer 8

• Convert food energy into
ATP
• Use ATP for body processes

Question 9

Direct Calorimetry (cost)

Answer 9

• Accurate method for measuring Energy expenditure
• It is expensive and impractical for humans
– Requires an individual to be in an insulated
chamber throughout the measurement

Question 10

Indirect calorimetry

Answer 10

Catabolic reactions break large molecules into
smaller units
– Energy in chemical bonds is released
– Energy is captured and stored in phosphate
bonds of ATP
• At the same time O2 is consumed and CO2 is
produced in a known ratio
• This is how energy expenditure is usually
measured in animals
• Device measures consumption of O2 and
expiration of CO2
– ATP production can be calculated from the
amount of CO2 expired & O2 inhaled

Question 11

Mammalian Energy Expenditure Components

Answer 11

• Basal Metabolic Rate (BMR)
• Thermic effect of food (TEF)
• Physical activity (PA)

Question 12

Basal Metabolic Rate (BMR)

Answer 12

• Energy for metabolism under basal conditions
• Involuntary activities of the body that are necessary for body
maintenance to keep you alive
– For example:
• Regulation of body temperature
• Nerve transmission
• Blood circulation

– Excludes:
• Physical activity
• Food digestion/absorption and processing
• Growth
• Represents 60 to 70% of total Energy expenditure

Question 13

BMR Measurement

Answer 13

• BMR measurement is taken
– After 12-hr fast
– In an awake, but calm state
– Thermoneutral conditions

Question 14

Resting Metabolic Rate

Answer 14

• RMR does not require a fasted state

* RMR is ~10% higher than BMR

Question 15

BMR Determinants

Answer 15

• BMR is directly proportional to lean body mass 
(LBM) or muscle mass
 – LBM is affected by 
   • Age
   • Gender
   • Body weight
   • Resistance Exercise
• BMR can rise with
  • Fever
  • Hyperthyroid function
• BMR can decrease as an adaptation to starvation

Question 16

Thermic Effect of Food (TEF)

Answer 16

• Increase in Energy expenditure after ingestion of food 
• Causes body temperature to rise slightly for some 
hours after eating 
• Metabolic cost of:
  – Digestion
  – Absorption
  – Metabolism
  – Storage of nutrients
• ~5 to 10% of Energy intake
  • A meal high in fat has a lower TEF

Question 17

Physical Activity (PA)

Answer 17

• Metabolic cost of external work
– Voluntary movements of the skeletal muscles and
support systems
• 2nd largest component of Energy expenditure
– ~15 to 30% of Energy expenditure
• Varies greatly with each individual
– NEAT (Non exercise Activity Thermogenesis) is the
energy expended for daily activities other than sleeping,
eating or sports-like exercise
– Has the most potential for change

Question 18

Energy Storage

Answer 18

– Excess Energy stored as Triglycerides (fat)
• Also some glycogen (carbohydrates)
– Energy stores come from macronutrients not used to
meet immediate Energy needs
– Stored energy is used when Energy intake is less than
Energy expenditure

Question 19

Ways to Estimate Energy Expenditure

Answer 19

• Standard Formulas
– RMR for individuals of same age, sex and
weight are fairly constant
•Weight can be used in a standard equation
– PA can be estimated from adding up energy
required for various activities
– TEF is ~ 10% of Energy intake

Question 20

Bioelectrical Impedence

Answer 20

A way to estimate energy expenditure.
– A method to determine body 
composition
– Uses a weak current to determine 
% body fat and lean body mass 
(LBM)
– More the muscle or lean body 
mass, the more the water 
associated with it
– Fat is a poor conductor of 
electricity, so it offers resistance to 
the current
• Can use LBM to predict BMR

Question 21

Body Mass Index (BMI)

Answer 21

• Body fat stores can also be estimated 
by evaluating weight for height
– BMI = weight in kg / (height in m)2
• BMI is a standard for evaluating body 
weight
– BMI correlates with body fat in 
most people
– It overestimates fat in people with 
a high muscle mass

Question 22

BMI Scale

Answer 22

• Healthy Weight
– 18.5 - 25
• Overweight
– 25 – 30
• Obese
– > 30

Question 23

Metabolic Hierarchy (Protein)

Answer 23

• Amino acids are used to meet the needs for
the synthesis of body proteins and non-
protein molecules first
• Any excess is then oxidized because there is
no mechanism for storing them as amino
acids or proteins

Question 24

Metabolic Hierarchy (carbs)

Answer 24

• Carbohydrates are used to maintain blood
glucose and to build glycogen stores
• Once glycogen stores are full, the remaining
Carbohydrates are oxidized for energy

Question 25

Metabolic Hierarchy (Fats)

Answer 25

• Dietary fat is first put 
into storage as TAG
• Fat is taken out of 
storage to meet the 
energy needs
  – Most fat that is 
  stored in the body 
  comes from 
  dietary fat

Question 26

Energy In Formula

Answer 26

BMR + TEF + PA +/- storage

Question 27

Hormone Leptin

Answer 27

• Long-term signal to tell body how much fat (stored
energy) it has
• Hormone produced by adipose tissue
– Produced in proportion to body fat
– Reduces appetite
•Higher fat causes more leptin to suppress appetite
– Increases Energy expenditure