Energy balance

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ENERGY BALANCE and ENERGY EXPENDITURE
M.Prasad NaiduMSc Medical Biochemistry, Ph.D,.
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Learning objectives

• Explain and discuss energy balance
• Energy intake
• Energy expenditure

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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

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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
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E.g.
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Energy intake

• One component of energy equation
• Energy sources
• CHO
• protein
• fat
• alcohol
• Diet assessment tools to estimate energy intake
• 24hr recall
• Food diaries

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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

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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

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• 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

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Principle of the doubly-labelled water method

• ii. Doubly labelled water (DLW)
• Utilizes water molecules containing stable
  isotopes of H2 and O2

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Components of Energy Expenditure (EE)

• Total Energy Expenditure (TEE)
• C1
• Resting Metabolic Rate (RMR)
• C2
• Thermic Effect of Activity (TEA)
• C3
• adaptive Thermogenesis (AT)

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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

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• 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

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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

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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

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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

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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)

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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

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Conclusion

• Energy balance
• Energy intake (CHO, protein, fat)
• Energy expenditure
• BMR or RMR
• TEA
• TEF
• AT

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THANK YOU