Energy Metabolism and Balance

Energy Metabolism and Energy Balance

• Key questions when it comes to conceiving the concept of energy balance:
  • What is measured when conducting energy expenditure measurements
  • What are the components of energy expenditure
  • What is the easiest method to increase energy expenditure
  • How to measure body fat
  • How does a treadmill or sport watch calculate expended energy
• The law of conservation must be considered
  • Total energy in the universe remains constant and conserved
  • Energy cannot be created or destroyed
  • Meaning the change of energy is the universe is zero
  • Energy can still be transferred from one substance to another, or converted to different forms
• A system is the part of the universe being observed
• Surroundings are everything else in the universe
  • System = reactants + products in the flask
  • Surroundings = flask + student + air + hand holding flask
• The 1st Law of Thermodynamics relates the universe, a system, and the surroundings
  • Any change in a system's energy is accompanied by an equal and opposite change in the surroundings
  • They counteract to maintain the universe's energy balance
  • Universe = System + Surroundings (Δ E universe = ∆ E system + ∆ E surroundings = 0)
  • Δ Ε system = - Δ E surroundings, or -Δ Ε system = Δ E surroundings
• Energy balance means energy put in will equal energy out
  • Energy intake (EI) = Total Energy Expenditure (TEE)
  • EI = EE ± Stored E

Resting Metabolic Rate and Energy Expenditure

• Resting energy expenditure utilizes the most daily energy
• A 70 kg person has a 2500 kcal TEE
  • 1500 kcal is attributed from Resting energy expenditure (REE/RMR)
  • 750 kcal is attributed from Activity-related energy expenditure (AEE)
  • 250 kcal is attributed from Thermogenesis of feeding (TEF)
• Rest energy allocated is used when at rest, this is the Resting Metabolic Rate (RMR)
• The RMR makes up 60% of daily energy expenditure
• Thermogenesis of feeding refers to the increase in energy expenditure that occurs after eating
  • The body uses uses energy to digest, absorb, and metabolize nutrients obtained from food
• Metabolic Adaptation refers to how the body adjusts energy expenditure based on changes in diet, activity or environment
  • Metabolism can either slow down or speed up depending on the body's need to maintain energy balance
  • Calorie restriction results in decreased metabolism to conserve energy
  • Calorie surplus results in increased metabolism to burn excess energy
  • Hormones such as thyroid hormones, leptin, and cortisol affect this
• Cells need energy and have their own metabolism and metabolic rate
• The brain's size and energy expenditure is prioritized over other functions
  • Even if it means decreasing energy use in other body parts.
  • The body prefers to give the brain more energy or maintain energy by using energy from other body parts
  • This is to ensure the brain continues to function properly

Work, Power, and Calorimetry

• Work is force multiplied by distance
  • Measured in Joules (J) = N/m (Newton per meter)
  • The SI unit is Joules
  • The American SI unit is kilocalories, 1 kcal = 4186 J or 4.186 kJ
• Power is work divided by time
  • Measured in J/sec (watt)
  • Power describes exercise intensity
• Work and power can be measured using ergometers
• Bench step exercises, cycle ergometers, and treadmills can measure work and power
  • For example taking a 30cm bench, stepping up and off at 30 steps a minute for 10 minutes
• Calorimetry:
  • Antione Lavoisier and Pierre Simon de Laplace built the first calorimeter, interested in measuring a guinea pig's heat production
  • The animal was placed in a compartment surrounded by ice
  • If respiration released heat, the ice would melt to release heat, producing heat internally
  • Measurement of the guinea pig's heat prouction was compared to heat produced burning charcoal
  • The guinea pig and charcoal used oxygen and produced carbon dioxide and heat like a combustion reaction

Respiration, Combustion, and ATP Production

• Respiration is a slow and controlled form of combustion
• The body burns food with oxygen to release energy
• Food provides macronutrients (carbs, fats, and proteins) for energy
• Water is essential for chemical reactions and maintaining balance
• Oxygen is used in aerobic respiration to burn food for energy (ATP)
• During aerobic respiration, an electron transfer occurs in the mitochondria through the electron transport chain (ETC)
• Oxygen is the final electron acceptor, and is therefore reduced to water
• As electrons move through the ETC, protons (H+ ions) are pumped across the mitochondrial membrane
• This creates an electrochemical gradient, like a battery, powering ATP production via ATP synthase
• The body consumes food and breathes in oxygen in order for cells to burn the food using oxygen, producing energy and water
• Macronutrients provide a specific amount of energy, but the energy isn't 100% available
  • Some is lost as heat during metabolism
  • Protein requires more processing as some energy is used to remove nitrogen in urea production
  • Fats take longer to break down but are energy-dense
  • Carbohydrates are efficient and nearly 99% of energy is usable
  • Alcohol is metabolized therefore all of it's energy is available
  • Proteins have the lowest efficiency because breaking them into amino acids and converting to energy is less direct

Chemical Equation for Energy Production and Thermodynamics

• Cellular respiration equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP + Heat)
  • Glucose (C6H12O6) is broken down
  • Oxygen (O2) is used to burn glucose
  • Carbon dioxide (CO2) and water (H2O) are produced as waste
  • Energy is released as ATP and heat
• Heat loss is why energy availability varies across macronutrients
• Energy cannot be created or destroyed
• Hess's Law states that the total enthalpy change for a reaction is the same, regardless of steps
  • Reactions in the body are exothermic, releasing heat
  • Energy change is independent of the pathway, depending on reactants and products
  • Supports The 1st Law of Thermodynamics, showing energy is conserved
  • This is like most of the reactions in our body

Measuring Energy Content and Expenditure

• Bomb calorimeters measures energy content of food
  • A food sample is burned in the precesence of oxygen in the reaction chamber, releasing heat energy
  • The heat warms the surrounding water, and the change in temperature is measured by a thermometer via the equation q = mc∆Т
  • The heat measured represents the energy stored in the food ( 1 kcal is the amount of energy to raise 1 kg of water by 1 degree. 1kcal = 4184 J)
  • Bomb calorimetry mimics oxidation in the body with macronutrients providing different amounts of energy
• Direct calorimetry systems features a calorimetric, closed chamber and measures energy expenditure
  • No external air or heat interferes with measurements
  • A water jacket circulates water that surrounds the chamber
  • Heat produced by the subject is transferred to the water
  • An increase in water temperature is recorded: 1 kilocalorie (kcal) raises 1 kg of water by 1°C
  • This directly measures heat and assesess total energy expenditure by tracking lost energy

Indirect Calorimetry and Respiratory Exchange Ratio

• Indirect calorimetry gauges energy expenditure by analyzing respiratory gases (oxygen consumption and carbon dioxide production)
• The system continously measures the subjects inhaled and exhaled air using special gas analyzers
• Key measurements and variables controlled
  • O2 and CO2 content of ambient air (air going in)
  • O2 and CO2 content of expired air (air going out)
  • Volume of expired air over time known as the ventilation rate
  • Temperature, pressure, humidity, and water vapor pressure
• VO2 measures Oxygen Consumption
  • It specifies how much O2 the body is using
• VCO2 measures Carbon Dioxide Production
  • It quantifies how much CO2 the body is producing
• These values help estimate energy expenditure and determine the Respiratory Exchange Ratio (RER)
• VO2 is the volume of O₂ consumed per minute (L/min): VO₂ = (V, × F/O₂) - (VEX FEO2)
• Both RER and RQ involve the ratio of carbon dioxide produced (VCO2) to oxygen consumed (VO2), but they are measured at different levels of metabolism
• Respiratory Exchange Ratio (RER) is the ratio of VCO2/VO2 measured at the lungs reflecting the whole-body metabolic fuel usage
  • RER can exceed 1.0 during intense exercise due to hyperventilation and bicarbonate buffering of lactic acid
  • After prolonged fasting, RER can drop below 0.7 due to increased fat oxidation

Respiratory Quotient, Calorimetry, and Energy Equivalents

• Respiratory Quotient (RQ) is the ratio of VCO2/VO2 measured at the cellular level
  • It represents the actual metabolic substrate being used in the mitochondria
• Both RER and RQ involve the ratio of carbon dioxide produced to oxygen consumed, but RER is volume measured at the lungs and RQ is the volume measured at the mitochondria
• The table outlines values in the cells
• VCO2/ VO2 Glucose: C6H12O6 + 6O2, RER = 1 6CO2 + 6H2O + 2817 kJ
• Fat palmitic acid C15H31COOH + 23O2, RER = 0.7 16CO2 + 16H2O + 10040 kJ
• Protein alanine 4CH3CH(NH2)COOH + 15O2, RER = 0.83
• 12CO2 + 14H2O + 2NH2 + 4 x 1623 kJ; yielding 2 moles of ammonia and is not completely oxidized
• Oxidation of nitrogen (2 mols) Urea cycle 2(NH2)2CO + 3O2, 2 CO2 + 4H2O + 2 N2 + 2 x 634.6
• Caloric Equivalents and Non-Protein RER
  • This table offers data on produced energy per litre of oxygen consumed from different macronutrients and differentiate caloric values for protein
  • kJ/L O2 is the energy (kJ) produced per litre of oxygen consumed.

Non-Protein RER and Key Assumptions

• Non-Protein RER is VCO2 from CHO + Fat / VO2 from CHO + Fat
  • It excludes protein metabolism and only considers the oxidation of carbohydrates and fats
• Protein oxidation is more complex, and its RER is variable due to nitrogen excretion
• High RER of >1.0 signifies overfeeding with carbohydrates which yields excess CO2 production and risk for ventilated patients
• Lower RER of ~0.8-0.85 signifies balanced energy use, including fat and protein oxidation
• RER close to 1.0 signifies the body is primarily burning carbohydrates
• RER near 0.7 signifies the body is primarily relying on fat oxidation
• A mixed diet results in an RER between 0.7 and 1.0
• Key assumtions in summary
  • The oxidation of fuels (carbohydrates, fats, and proteins) is the primary source of energy for predictable ratios of O2 consumed to CO2 produced. All O2 is consumed, and ALL CO2 is produced as a result
  • The body is in a metabolic steady state as gas exchange is in non-acidotic, steady-state, conditions
  • Energy expenditure calculation and preciion relied on O2 and CO2 measurements volumes and concentrations
  • Calculations assume that aerobic metabolism is the primary energy source

Doubly Labeled Water and Food Quotient

• The Doubly Labelled Water (DLW) measures total energy expenditure in free-living humans and animals over an extended period of time
  • It tracks two stable isotopes: 18O oxygen-18 and 2H deuterium in body water
• The subject drinks water labelled with deuterium and oxygen-18, and these isotopes mix and equilibrate
• Oxygen-18 is eliminated in both Carbon Dioxide and water, while deuterium only exists in water
• The variance in elimination determines carbon dioxide production rate
• Saliva, urine or blood samples are taken at Day 1 (baseline) and Day 14 for isotope turnover
• The Carbon Dioxide production assesses Total energy expenditure using macro oxidation
• Diet is a mixed average that averages 23.5 kJ of the produced CO₂
• Measurements by the DLW are VCO2 which is how much carbon the body has, yet VO₂ has an precise measurement

Determining Food Quotient and Relating Heart Rate to Energy Expenditure

• Food quotients estimate oxygen use
• It is a theoretical VCO₂ / VO₂ value from foods being fully oxidised
• Substituting RER with the with (FQ) only becomes possible when the diet if stable
• VCO₂ = (VO₂ / FQ) Is the product of when oxygen can be measured
• TEE is an estimate when using energy divided by a span of free range state
• The metabolic chamber are more accurate towards the data and method, but the exercise can be tough
• Heart rate increases with energy and expenditure (kcal/min)
• Lower <100 bpm results in light activity
• Higher >120 bpm results in modate to vigours activity
• Heart rates and energy have an interrelationship by activity

Estimating Energy Expenditure and Limitations of Using HR

• A graph illustrates how estimated energy expenditure correlates with observed EE to determine the accuracy of heart rate-based prediction in measuring real energy use
  • X-axis represents actual energy expenditure
  • Y-axis represents the usage of heat rate data
  • Each dot measure EE, comparing the observed the precited values
  • Lines determine between estimated and observed EE are accurate
• The means of the heart rate indicates 81% is correlated to measuring and indicates its accurately
  • HR can indicate individual factors with metabolism, Movement or enviromental
• The use of HR to determine someone accurate on there 02 consumption
• It can differ with the way they are trained and in doing will require someone to train for such task
• It happens due changes within someone such as posture, emotion or to ones enviromental conditions
• If low on one energy, heart rate does not increase
• Results of heart rate is dependent on modern -vigoours actives that show limitations

Accelerometer and its Cut Points

• An accelerometer measures a small electrical device for measuring
  • Overall movement, Prolong inactivity & energy
• It measures human movement from acceleration of velocity over time
• It may have axis with multiple directs to a plain
  • Can be unaxial, biaxial or triaxial
• Objective movement data to measure body temperature, posture or emotions
• Used for heath monitor, fitness activity and tracking
• Threshold values classify and activity with it accelerometer that correspond for intensity that
• Light moderate of vigours cut off for act ivies with amount with accelerate
• The study with accelerometer is measured on adult and child cut off population

Energy Expenditure and Fat-Free Mass Relationship

• Researchers provide varios cut points with help to estimates that are
• Freedon, Colluey and values at MET
• Person same weight can have different expenditures
• Mass will have RMR that is more on someone to someone fatness.
• Mass to rest is the equation to have them have strong relationships
• Has males with ffm that cause someone to require more rest

FFM Measures and Thermic Effect of Food

• Skin fold gauge thickness of calipers
• Air replacement estmates the chambers air of person body
• Density measures under waters bodies measured is the volume
• Resistance of electrical determines the fat percentile from low content current
• (DEXA) uses x-rays that seperate soft tissues to help fat mass and body to distribute
• Wais measures the fatness and measure at hip area to be tested
• There good data collected from water scans, to test some one ffm that show test full bodies
• Only test can have is there (MR/BMR) with there muscles
• Affect means the increase for energy to have the the baseline
• Method is by being calorie
• TEE is used from energy intake at its rate that is the bodies fat

Insulin Resistance, Thermic Effect, and Whole Foods

• Protein has The highest amounts of heat due from the digestion of there metabolic protein
• A protein can loose most amount at a level for there intake
• Have the chart to help the high protein with is over the time
• The graph was being able to show is high for DIT from diet
• Can control and show this result but on graph
• The food can increase the fuel better for the ones that protein
• The rate for protein increase with basel to full up
• Affected increase on themetic food
• Can help and to loose for metabolic level of food
• Whole foods for the body for digertion and absortion of metabolic process
• The more they all need there energy with the process to digerted with energy and fuel

Exercise, Sympathetic Activity, and Adaptive Thermogenesis

• Food increases a person energy with proccess foods add for potentially more weight then what gained
• Habitercial Exercies add the greater of symatic with actitives
• Lead to higher to the ones that is sedately is the individual
• Respond with greater with metabolic balance
• Indvidulas loose response to lower the way for a persons metabolic rate
• Regular exercises that is metabolic to help for regulate bodys weight to help

Thermogenesis, Low Energy Expenditure, and Ketones

• TEF can be have for affect a few factors that was from the study
• Exercise assist with the effects of an increasing energy (E1) with stored energy for essential weight loss
• Low fats with exercise by (FFAD5)
• Levels have occur more with metaolic rate
• The fatty can occur more from the toxins with fats and tissues
• Take is needed for more uptake of the ffa in working muscles will help to prevent the affect of accumulation in the blood

Occuptional Energy Expenditure and Oxygen Consumption

• Ocupalined is declines in occuptialned energu with the expenitures
• The rate or the mean decrease that will cause with contributor too overall to people physic with activities
• Shows the graphs that rate that women weight over the high number for the years
• More physical activity and to the working rate to have a key for obesity
• Glucose shows more highest percentage to end
• The expennditure requires someone for a longer body for steady rate

Lower/Higher Intensities and Crossover Concept

• Increase hard and takes a little bit for the total body to level oxyen
• Less intense allow stability to help with energy demands
• Higer intense require adjust from body for oxygen and cardio that can adapt
• If intensity is to high steady ,ay even not be reached
• Shifting the body to rely to switch between different fuel sources of fatty
• The has body shifts to energy rate intensity increases and fat
• Looser with activity to use a primly source fuel at (fat) in a way that the rate changes for energy source
• Increase with activity for increase body by higher source on (CHO) of the rate that energy
• Adaptable on what the crossover rate can change within someone to help
• The exercise with (fat activity) with an upper level of rate with carbon fuel
• While increase, burns off the high fat better due to upper lev for total energy that it it helps

Fat Use in Trained Athletes, Free Fat Mass, and Exercise Effects

• The endure to increase for fats
• ~25% the glyocen have the body is may shift to more fats
• The adaptation was seem too have that the free replimshmeent with date that is stated in debt
• Endo to prove the fast metatolism that more the to has the long remain as uncertant
• Increase the predict of amount as (EE)