Energy Balance Flashcards
(23 cards)
What is energy?
It is the capacity to do work.
Give the 2 methods of measuring energy in food. Explain the difference between the two.
Direct - using a calorimeter
Indirect - using the food composition table and oxycalorimetry
How many joules is in 126 kcal?
1 kcal/cal = 4.184 J
126 kcal x 4.184 J/1 kcal = 527.184 J or 527 J
Who pioneered bomb calorimetry?
Antoine Lavoisier
Explain the concept of bomb calorimetry in one sentence.
The amount of energy released by carbohydrate or fat when burned is the same as the amount of energy metabolized by the body when ingested.
Implication of bomb calorimetry.
Energy in food (cal) is the amount of energy produced in the body via food metabolism.
Which macronutrient has the least %Digestibility?
Protein
CHO: 98%
PRO: 92%
Fat: 95%
It is defined as the ratio of carbon dioxide production to oxygen consumption.
Respiratory Quotient (RQ)
The method of measuring energy in food that estimates energy expenditure via determination of O2 consumption and CO2 production in a given time period.
Indirect calorimetry
A modification of the respiratory chamber that uses thermocouples and a heat exchange disc attached to the subject’s skin.
Metabolic chamber
A method of measuring energy in food by measuring heat given off by the body using a respiratory chamber.
Direct calorimetry
Give the RQ of Fat
Fat RQ = 0.70
Among the three macronutrients, which has the highest RQ?
Carbohydrates
CHO RQ = 1.00
PRO RQ = 0.82
Fat RQ = 0.70
Differentiate: Direct calorimetry and Indirect calorimetry
Direct calorimetry measures the heat released (energy used) by the body using a respiratory chamber whereas indirect calorimetry only estimates energy used by the body via determination of oxygen consumption and carbon dioxide production in a given time frame.
Enumerate the three components of energy expenditure.
- Basal Metabolic Rate (BMR)
- Physical Activity (PA)
- Thermic effect of food (specific dynamic activity of food)
Which among the three components of energy expenditure has the highest percentage relative to TEE?
Basal Metabolic Rate: 60-65%
What are the different parts of a bomb calorimeter and their respective functions?
Oxygen supply = provides oxygen
Ignition wires =
Stirrer = equalize temperature of water
insulating jacket = ensures that the system is closed
bucket = contains the water
heater =
water =
air space = separates the water from the insulating jacket
crucible = sample container
steel bomb = separates the water from the sample
ignition coil = provides heat
magnifying eyepiece =
thermometer =
What is the energy value of food determined byte the bomb calorimeter referred as? It is also the maximum amount of energy, measured as heat, which the food is capable of yielding under controlled conditions that favor complete oxidation.
Heat of combustion
Give the two reasons why the human body is not efficient in utilizing food for energy.
- The body cannot digest, absorb, and metabolize nutrients efficiently at 100%. This means that the extent to which the ingested food is available for the cell must be taken into account to determine the energy available from the source.
- Metabolizable energy or the physiological fuel value. Carbs, fat and alcohol are oxidized completely in cellular metabolism but nitrogen from protein is not resulting in a 1.25 kcal/g of protein lost.
This method of determining the amount of heat produced by the body is done by measuring the change in temperature of a known volume of water circulating in pipes at the top of the chamber. It is expensive and only few calorimeters for this method are available globally.
Respiratory chamber
True or False: A patient with an RQ of 1.00 is underfed.
False. An RQ of 1.0 means that the body is dependent on carbohydrate stores for energy. When carbohydrates are utilized, this means that there is enough carb source in the body and the patient is either well-fed or overfed. Underfeeding results in a low RQ.
True or False: Thermic Effect of Food (TEF) or Dietary-Induced Thermogenesis was earlier known as Specific Density Action (SDA)
False. Specific Dynamic Action
Differentiate: Basal Metabolism and Basal Metabolic Rate
Basal Metabolism refers to the energy requirements of of physiological activities during the post-absorptive state. Meanwhile, basal metabolic rate refers to the rate at which the body spends energy for the maintenance of physiological activities.
TLDR, basal metabolism talks about energy requirement at rest while BMR is the frequency of energy expenditure for the maintenance of physiological activities.
