Chapter 6

 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.

 Joule or Kilojoule  Standard international unit expressing energy  1 cal = J  1 kCal = 1000 cal = 4186 J = kJ  Megajoule  1000 kJ

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

 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

 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

 Atwater – chemist  Actual energy available to the body  Coefficient of digestibility Affected by dietary fiber Atwater general factors  Carbohydrates: 4  Lipids: 9  Proteins: 4

 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.

 Energy expenditure  Measurements of oxygen uptake and carbon dioxide production using: Closed-circuit spirometry Open-circuit spirometry

 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

 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

 RQ equals  1.00 for carbohydrate,  0.70 for fat,  0.82 for mixed diet

 Carbohydrate ◦ C 6 H 12 O O 2 → 6 H 2 O + 6 CO 2 ◦ RQ = 6 CO 2 / 6 O 2 ◦ RQ = 1.00

 Lipid ◦ C 16 H 32 O O H 2 O → 16 H 2 O + 16 CO 2 ◦ RQ = 16 CO 2 / 16 H 2 O ◦ RQ =.696 (.70)

 Ratio of carbon dioxide produced to oxygen consumed  Measured at the mouth (expired gases)  Computed in exactly the same manner as RQ  VCO 2 /VO 2  Not as effective in determining substrate use as some CO 2 from buffering lactic acid (Non- metabolic CO 2 production) can raise RER

 R above 1.00 Hyperventilation due to acidosis Exhaustive exercise  Lactic acid  HLA + NaHCO 3 → NaLa + H 2 CO 3 → H 2 O + CO 2

 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

BMR measurement (metabolic cart)  No food or exertion – 12 h  Following min quiet rest Resting metabolic rate  Awake, moving around

 Energy expended during physical activity and recovery Physical activity  Accounts for between 15% and 30% total daily energy expenditure (TDEE)

 Thermogenic influence of food consumed Dietary-induced thermogenesis  Can influence metabolic rate substantially  Energy of digestion

 Climate Tropical  5-20% higher RMR Hot environment  Additional metabolic load Cooling body

 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 =