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ENERGY BALANCE

BIOCHEMISTRY

mprasadnaidu
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ENERGY BALANCE

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  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 (%) = energy intake (kcal)/energy expenditure (kcal) * 100% • 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

  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 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. 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 • 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

  20. THANK YOU

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