energy balance
DESCRIPTION
SUPERTRANSCRIPT
ENERGY BALANCE and ENERGY EXPENDITURE
M.Prasad NaiduMSc Medical Biochemistry, Ph.D,.
Learning objectives Explain and discuss energy balance
Energy intake
Energy expenditure
Energy balance Relationship between level of energy intake
and expenditureEnergy intake
○ Energy absorbed and maintained by bodyEnergy expenditure
○ Energy used in cellular metabolism or lost from excretory routes
Occurs when energy intake matches energy expenditure
Energy balance equation
Energy balance can eitherNil
○ 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 Energy balance (%) = energy intake (kcal)/energy expenditure
(kcal) * 100%(kcal) * 100%
E.g.
Energy intake One component of energy
equationEnergy sources
○ CHO○ protein ○ fat
alcohol
Diet assessment tools to estimate energy intake24hr recallFood diaries
Energy expenditure Other component of energy balance equation
Energy nutrients (CHO, fat, protein) broken down in tissue to power muscle contractions and other cell activitiesResulted 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
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 periodand heat dissipated by body is measured
○ MechanismHeat release warms a layer of water or other fluid surrounding
chamber, and change in fluid temp reflects person’s energy expenditure
Indirect calorimetryi. Metabolic cart that measures VO2 and VCO2
○ where tubing connects to person while at rest or engaged in physical act
○ MechanismVolume 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
ii. Doubly labelled water (DLW)Utilizes water
molecules containing stable isotopes of H2 and O2
Principle of the doubly-labelled water method
Components of Energy Expenditure (EE) Total Energy Expenditure (TEE) =
C1 ○ Resting Metabolic Rate (RMR) +
C2○ Thermic Effect of Activity (TEA) +
C3○ adaptive Thermogenesis (AT)
C1: Basal and RMR Basal metabolism (BM)
energy expended during nonactive restMeasures 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 interchangeablyRestricts 4 hrs after meal prior to assessment or later in
day10% more than BMR
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
BMR estimation Method 1. Basal energy
BMR=BWx24hrs
Method 2. BMR = 70 x BW75
Method 3. Harris-Benedict formulaMen (BMR)=66+(13.7xBW)+(5xht)-(6.8xage)Women (BMR)=655+(9.6xBW)+(1.7xht)-(4.7xage)
Method 4. FAO/WHO EquationMale (30-60)=11.6xwt+487Female (30-60)=10.5xwt+596
BMR comparison
Male has higher BMR to female due to greater skeletal muscle to adipose tissue ratioGender 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
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
C3: Thermal Effect of Food (TEF) Increase in energy expenditure associated with
consumption of foodRepresents 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 bySize (larger – more TEF)Composition of meals (more CHO and protein-more
TEF)
C4: Adaptive Thermogenesis (AT) Energy expenditure increase and even
decrease due to change in environmental tempt and exposure to radiant energyManipulate energy expenditure to regulate body
tempt
E.g. applicable to travel athletes to cool environment, etc
Conclusion
Energy balance
Energy intake (CHO, protein, fat)
Energy expenditure○ BMR or RMR○ TEA○ TEF
AT