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Measurement of Energy in Food and During Physical Activity

Measurement of Energy in Food and During Physical Activity. Chapter 6. Units of Energy. Calorie One calorie expresses the quantity of heat necessary to raise the temperature of 1 g of water by 1° Celsius. Kilocalorie (kCal)

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Measurement of Energy in Food and During Physical Activity

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  1. Measurement of Energy in Food and During Physical Activity Chapter 6

  2. Units of Energy • Calorie • One calorie expresses the quantity of heat necessary to raise the temperature of 1 g of water by 1° Celsius. • Kilocalorie (kCal) • One calorie expresses the quantity of heat necessary to raise the temperature of 1 kg (1 L) of water by 1° Celsius.

  3. Units of Energy • Joule or Kilojoule • Standard international unit expressing energy • 1 cal = 4.186 J • 1 kCal = 1000 cal = 4186 J = 4.184 kJ • Megajoule • 1000 kJ

  4. Temperature Versus Heat • Temperature reflects a quantitative measure of an object’s hotness or coldness. • Heat describes energy transfer from one body or system to another.

  5. Bomb Calorimeter • Measures total energy value of foods • Type of calorimetry • Direct • Measures heat liberated as food burns • Sealed chamber • Oxygen, under pressure • Surrounded by water jacket • Increase in water temperature directly reflects the heat released during a food’s oxidation. • Heat of combustion

  6. Bomb Calorimeter

  7. Heat of Combustion • Carbohydrates • Glucose = 3.74 kCal/g • Glycogen = 4.19 kCal/g • Average = 4.2 kCal/g • Lipids • Beef, pork fat = 9.5 kCal/g • Butterfat = 9.27 kCal/g • Average = 9.4 kCal • Proteins • Beans = 5.75 kCal/g • Average = 5.65 kCal

  8. Net Energy Value • Atwater – chemist • Actual energy available to the body • Coefficient of digestibility • Affected by dietary fiber • Atwater general factors • Carbohydrates: 4 • Lipids: 9 • Proteins: 4

  9. Direct Calorimetry • Directly measures energy expenditure • Human calorimeter • Airtight chamber • A person lives or works in the chamber for an extended period of time. • Changes in water temperature relate directly to an individual’s energy metabolism.

  10. Direct Calorimetry

  11. Indirect Calorimetry • Energy expenditure • Measurements of oxygen uptake and carbon dioxide production using: • Closed-circuit spirometry • Open-circuit spirometry

  12. Indirect Calorimetry • Closed-circuit • Subject breathes 100% oxygen from a prefilled container. • A canister of soda lime absorbs the carbon dioxide in exhaled air. • Open-circuit • Subject inhales ambient air • Indirectly reflects energy metabolism

  13. Closed or Open Circuit Spirometry

  14. Portable Spirometry

  15. Bag technique

  16. Computerized Instrumentation

  17. Respiratory Quotient (RQ) • The ratio of carbon dioxide produced to oxygen consumed • Measured at the exercising muscle • Reflects cellular respiration • Rest and Steady state • The RQ provides information about the nutrient mixture catabolized for energy. • Carbohydrate • Fat

  18. Respiratory Quotient (RQ) • RQ equals • 1.00 for carbohydrate, • 0.70 for fat, • 0.82 for mixed diet

  19. Respiratory Quotient (RQ) • Carbohydrate • C6H12O6 + 6 O2 → 6 H2O + 6 CO2 • RQ = 6 CO2 / 6 O2 • RQ = 1.00

  20. Respiratory Quotient (RQ) • Lipid • C16H32O2 + 23 O2 + 6 H2O → 16 H2O + 16 CO2 • RQ = 16 CO2 / 16 H2O • RQ = .696 (.70)

  21. Respiratory Exchange Ratio (RER) • Ratio of carbon dioxide produced to oxygen consumed • Measured at the mouth (expired gases) • Computed in exactly the same manner as RQ • VCO2/VO2 • Not as effective in determining substrate use as some CO2 from buffering lactic acid (Non-metabolic CO2 production) can raise RER

  22. Respiratory Exchange Ratio (RER) • R above 1.00 • Hyperventilation due to acidosis • Exhaustive exercise • Lactic acid • HLA + NaHCO3→NaLa + H2CO3→ H2O + CO2

  23. Total Daily Energy Expenditure • Factors that determine total daily energy expenditure (TDEE): • Basal metabolic rate – minimum energy requirement to sustain cellular respiration • Decreases with age • Slower decline with exercise • Lower in females than males

  24. Total Daily Energy Expenditure • BMR measurement (metabolic cart) • No food or exertion – 12 h • Following 30-60 min quiet rest • Resting metabolic rate • Awake, moving around

  25. Total Daily Energy Expenditure • Energy expended during physical activity and recovery • Physical activity • Accounts for between 15% and 30% total daily energy expenditure (TDEE)

  26. Total Daily Energy Expenditure • Thermogenic influence of food consumed • Dietary-induced thermogenesis • Can influence metabolic rate substantially • Energy of digestion

  27. Total Daily Energy Expenditure • Climate • Tropical • 5-20% higher RMR • Hot environment • Additional metabolic load • Cooling body

  28. The Metabolic Equivalent (MET) • One MET represents an adult’s average seated, resting oxygen consumption or energy expenditure. • Convenient way to rate exercise intensity • 1 MET = 3.5 mL/kg/min • 1 MET represents an energy expenditure of ~1.2 kcal/min for 70 kg person • 5 METs =

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