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Dr.M.Prasad Naidu, profile picture
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Energy Balance

Energy balance occurs when energy intake from food matches energy expenditure by the body. Energy expenditure consists of basal metabolic rate (BMR), the energy required for basic body functions, thermic effect of activity and food, and adaptive thermogenesis. BMR accounts for 50-75% of total energy expenditure and can be estimated using formulas factoring in weight, height, age, and gender. Tracking energy intake and expenditure helps determine if a person has a surplus, deficit, or balance of calories.

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ENERGY BALANCE and ENERGY EXPENDITURE M.Prasad Naidu MSc Medical Biochemistry, Ph.D,.
Learning objectives  Explain and discuss energy balance Energy intake Energy expenditure
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
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%
E.g.
Energy intake  One component of energy equation Energy sources ○ CHO ○ protein ○ fat alcohol  Diet assessment tools to estimate energy intake 24hr recall Food 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 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
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
 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
 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 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
 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 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
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
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 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)
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
Conclusion  Energy balance Energy intake (CHO, protein, fat) Energy expenditure ○ BMR or RMR ○ TEA ○ TEF AT
Energy Balance