Energy balance occurs when energy intake from food matches energy expenditure by the body. Energy expenditure consists of basal metabolic rate (BMR), the energy required for basic body functions, thermic effect of activity and food, and adaptive thermogenesis. BMR accounts for 50-75% of total energy expenditure and can be estimated using formulas factoring in weight, height, age, and gender. Tracking energy intake and expenditure helps determine if a person has a surplus, deficit, or balance of calories.

1. ENERGY BALANCE
and
ENERGY EXPENDITURE
M.Prasad Naidu
MSc Medical Biochemistry, Ph.D,.

2. Learning objectives
 Explain and discuss energy balance
Energy intake
Energy expenditure

3. Energy balance
 Relationship between level of energy intake
and expenditure
Energy intake
○ Energy absorbed and maintained by body
Energy expenditure
○ Energy used in cellular metabolism or lost from
excretory routes
 Occurs when energy intake matches energy
expenditure

4. Energy balance equation
 Energy balance can either
Nil
○ No change in energy status and weight
+ve
○ Energy surplus and potential increase in body weight
-ve
○ Energy deficit and potential body weight reduction
Energy balance (%) = energy intake (kcal)/energy expenditure (kcal) * 100%Energy balance (%) = energy intake (kcal)/energy expenditure (kcal) * 100%

5. E.g.

6. Energy intake
 One component of energy
equation
Energy sources
○ CHO
○ protein
○ fat
alcohol
 Diet assessment tools to
estimate energy intake
24hr recall
Food diaries

7. Energy expenditure
 Other component of energy balance equation
 Energy nutrients (CHO, fat, protein) broken down
in tissue to power muscle contractions and other
cell activities
Resulted in energy released from body in the form of
heat energy (kcal)
1kcal of heat energy
○ Amount of heat required to raise temp of 1kg of H2O by 1o
C =
4.184 kj
Metabolic rate describes amount of energy released in
a given unit of time

8. Tools for assessment of energy expenditure
 Direct calorimetry
Metabolic chamber
○ by measuring amount of gases utilized and produced
during energy metabolism directly
○ where a person enters an insulated room or metabolic
chamber for a specific period
and heat dissipated by body is measured
○ Mechanism
Heat release warms a layer of water or other fluid surrounding
chamber, and change in fluid temp reflects person’s energy
expenditure

9.  Indirect calorimetry
i. Metabolic cart that measures VO2 and VCO2
○ where tubing connects to person while at rest or
engaged in physical act
○ Mechanism
Volume of CO2 produced is divided by volume of O2 consumed
to yield respiratory exchange ration (RER)
- RER
- used to predict the contribution made by fat and CHO to total
energy experiment, because oxidations of these nutrients are
associated with different ratios of VO2 and CO2
- now used in weight management programms to better predict
energy expenditure for diet prescription

10.  ii. Doubly labelled
water (DLW)
Utilizes water
molecules
containing stable
isotopes of H2 and
O2
Principle of the doubly-labelled water method

11. Components of Energy
Expenditure (EE)
 Total Energy Expenditure (TEE) =
C1
○ Resting Metabolic Rate (RMR) +
C2
○ Thermic Effect of Activity (TEA) +
C3
○ adaptive Thermogenesis (AT)

12. C1: Basal and RMR
 Basal metabolism (BM)
energy expended during nonactive rest
Measures in a climate-controlled room 12 hrs after a
meal
 Basal metabolic rate (BMR)
Basal metabolism during specific period e.g. 1 hour or
1 day
 Resting metabolic rate (RMR)
Used interchangeably
Restricts 4 hrs after meal prior to assessment or later

13.  BMR or RMR
Is related to homeostasis including energy
expended for cell turn over, resting heart rate and
respiration, urine production, protein synthesis,
nucleic acid, etc
About 50-75% or 60-75% of TEE is BMR or RMR
respectively

14. BMR estimation
 Method 1. Basal energy
BMR=BWx24hrs
 Method 2.
BMR = 70 x BW75
 Method 3. Harris-Benedict formula
Men (BMR)=66+(13.7xBW)+(5xht)-(6.8xage)
Women (BMR)=655+(9.6xBW)+(1.7xht)-(4.7xage)
 Method 4. FAO/WHO Equation
Male (30-60)=11.6xwt+487
Female (30-60)=10.5xwt+596

15. BMR comparison
 Male has higher BMR to female due to
greater skeletal muscle to adipose
tissue ratio
Gender differences in O2 consumption (VO2)
○ Women consume ~80% of what men
consume
 Infant has higher BMR to adults due to
greater % of FFM than adults and
engaged in rapid tissue growth

16. C2: Thermic Effect of Activity (TEA)
 This is the skeletal muscle
activity where more ATP
demand is required for both
muscle contraction and
relaxation
 In addition to physical
movement as walking, talking,
running, climbing stairs and
maintaining positions and
posture
 Estimation of TEA can be
done by keeping an activity
log over a 24hr period
 then apply energy equivalent
coefficients in the following
table

19. C3: Thermal Effect of Food (TEF)
 Increase in energy expenditure associated with
consumption of food
Represents increase in TEF attributed to digestion,
absorption, metabolism and storage of nutrients
Estimated to be 10% of TE intake during a day
○ E.g. 250kcal from 2500kcal over a 24hr period
 TEF may also be influence by
Size (larger – more TEF)
Composition of meals (more CHO and protein-more
TEF)

20. C4: Adaptive Thermogenesis (AT)
 Energy expenditure increase and even
decrease due to change in environmental
tempt and exposure to radiant energy
Manipulate energy expenditure to regulate body
tempt
E.g. applicable to travel athletes to cool
environment, etc

21. Conclusion
 Energy balance
Energy intake (CHO, protein, fat)
Energy expenditure
○ BMR or RMR
○ TEA
○ TEF
AT