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Energy Balance


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  • 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
  • 17. 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)
  • 18. 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
  • 19. Conclusion  Energy balance Energy intake (CHO, protein, fat) Energy expenditure ○ BMR or RMR ○ TEA ○ TEF AT