Energy balance - PowerPoint PPT Presentation

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Energy balance

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Title: Energy balance


1
ENERGY BALANCE and ENERGY EXPENDITURE
M.Prasad NaiduMSc 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
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 1oC 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 persons 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
Principle of the doubly-labelled water method
  • ii. Doubly labelled water (DLW)
  • Utilizes water molecules containing stable
    isotopes of H2 and O2

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 in day
  • 10 more than BMR

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
  • BMRBWx24hrs
  • 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)11.6xwt487
  • Female (30-60)10.5xwt596

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

17
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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

22
THANK YOU
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