What is the difference between kcal and kJ?
- they are inequivalent units of measure used to express energy
1 calorie =
4.184 joule
4 steps of energy metabolism:
- food
- digested
- absorbed
- metabolized/oxidized
Macronutrients are oxidized by creating _____, which is….
- ATP
- major storage form of molecular energy in our body
When a molecule is oxidized, a significant portion of the release energy is salvaged as ____ ____ in the form of …..
- chemical energy
- new, high energy bonds, with the rest released in the form of heat
The chemical energy is generally contained in ____ ____ ____ ____, chiefly those of _____.
- high energy phosphate bonds
- ATP
In the 1950s, what did Rubner & Atwater find?
- metabolizable energy
- difference between the gross energy of consumed food and the energy present in feces and urine
Metabolizable energy:
amount of fuel actually available to cells for conducting biological processes
Atwater had begun to analyze the _____ and ____ ____ of food.
- composition
- energy content
One of the largest and most comprehensible databases for energy metabolism is:
USDA National Nutrient Database
Canada’s database:
Canadian Nutrient File
PRO = ___ kcal/g
4
CHO = ____ kcal/g
4
FAT = ___ kcal/g
9
3 components of total energy expenditure (TEE):
- resting metabolic rate
- activity thermogenesis
- thermic effect of food
Expended energy reflects fuels metabolized for ….
- growth
- body maintenance needs
- PA
- pregnancy and lactation
- other processes
Key determinants of activity EE:
- genetic traits
- age
- sex
- environmental stimuli
Key determinants of thermal effect of food:
- diet composition
- age
- PA
- obesity
- insulin resistance
Key determinants of resting metabolic rate:
- fat free mass
- fat mass
- sex
- age
- genetic traits
RMR:
- resting metabolic rate
- energy required for the maintenance of normal body functions and homeostasis in resting conditions
RMR accounts for ___% of TEE.
60-70
Different ____ ____ have markedly different resting energy requirements.
body tissues
Organs that have large metabolic demands:
- liver
- kidneys
- intestines
- brain
- heart
- these organs together: 10% of total body weight and 75% of RMR
Adipose tissue EE:
- 20% of total body weight
- < 5% of RMR
Skeletal muscle EE:
- 40% of total body weight
- 20% of RMR
RMR correlates closely with _____.
FFM
Although EE of metabolically active _____ is responsible for a large component of RMR, _____, which is composed primarily of ____ ____, accounts for most of the variability in EE between individuals.
- organs
- FFM
- skeletal muscle
Contrary to popular belief, people with obesity generally have a _____ absolute resting EE. Why?
- higher
- higher PA expenditure
- higher resting EE
- higher thermic effect of food
REE is linearly related to both ____ and ____.
- FFM
- FM
People with obesity have higher ___ and ___.
- FFM
- FM
FFM = ______ active tissues, contributes more to _____.
- metabolically
- REE
2 components of activity thermogenesis (AT):
- exercise activity thermogenesis (EAT)
- non-exercise activity thermogenesis (NEAT)
EAT:
EE of a planned, structured, and repetitive PA with the objective of improvement or maintenance of physical fitness
NEAT:
EE of any bodily movement produced by skeletal muscles
The most variable component of daily EE is…
AT
AT can vary from an average of ___% of the daily EE up to ____% in extreme conditions during heavy ____ training or competition.
- 30%
- 80%
- endurance
_____ is extremely important for the maintenance of the daily energy balance.
exercise
AT can be controlled ______.
voluntarily
_____ is very high in active individuals, where as _____ is very high in sedentary individuals.
- AT
- RMR
However, in contrast to the predictions of the constrained EE model….
- exercise training does not lead to dec. REE under conditions of weight stability
- REE adjusted for body composition is not equal to between people with a wide range of PA levels
- exercise may increase the TEF
When PA increases via exercise, the non-PA components of EE…..
do not decrease as predicted by the constrained model
Increments in daily EE shortly after starting an ____ ____ can be greater than the expended energy cost of the exercise.
exercise program
As training progresses, daily EE does not _____ ____ (despite increasing volume and intensity) –> may be because of improvements in ____ _____ that decrease energy cost of exercise.
- increase linearly
- biomechanical efficiency
Diets differing in ____ ____ could result in different responses on energy metabolism.
macronutrient distribution
Energy balance =
body weight maintenance
One of the first studies in dietary manipulation took place in _____.
1957
Weight loss in people with obesity was intimately related to _____ _____ of the diet.
macronutrient composition
Trends in CHO, FAT, and PRO intake:
- inc. energy CHO + dec. PRO, FAT = inc. obesity
- 1% inc. protein = dec. 32 kcal CHO & dec. 51 kcal FAT
Increasing PRO composition of diet may facilitate ____ _____ _____.
reducing energy intake
Isocaloric diets differing in macronutrient composition may result in …. This over the long term will alter….
- preferential partitioning of energy storage
- the proportions of FM and FFM during weight loss and weight gain
Dietary ____, in particular, is known to positively influence ___ during weight loss and weight gain.
- protein
- FFM
Energy balance refers to the balance between…
EE (RMR, AT, TEF) and energy intake (Kcal, macronutrients)
Negative energy balance:
- EE > intake
- weight loss
Positive energy balance:
- intake > expenditure
- weight gain
RQ:
- respiratory quotient
- directly measured from tissues (invasive)
- provides meaningful information with respect to EE and substrate oxidation
RQ =
VCO2/VO2
RER:
- under steady-state conditions, we measure VO2 and VCO2 from the mouth (indirect calorimetry)
- predicts well what is happening at the cellular level (less invasive)
An RQ = 1.00 suggests….
- CHO is being oxidized
- the amount of O2 required for the combustion of glucose equals the amount of CO2 produced
An RQ = 0.70 suggests….
- FAT is being oxidized
- fatty acids are a much less oxidized fuel source (fewer O2 molecules)
An RQ for _____ is more complicated….
- protein
- metabolic oxidation of AA requires removing the N and some O2 and C as urea
- urea N represents a net loss of energy to the body: only the C chain can be oxidized in the body
An RQ of 0.82 suggests…..
PRO is being oxidized
If a truly accurate RQ is required, a correction has to be made by measuring the amount of ____ ___ _____ over a specific time period.
Urinary N excreted
For every 1g of N excreted:
- 5.912 L of O2 are consumed
- 4.758 L of CO2 are produced
The amount of O2 and CO2 exchanged in the release of energy from ____ can be subtracted from….
- protein
- the total amount of measured gaseous exchange
The RQ of an ordinary mixed diet consisting of CHO, PRO, and FAT is usually….
0.85
In clinical practice, an RER < 0.70 can indicate:
- hypoventilation
- underfeeding
- alkalosis
- ketosis
- low-carb diet
- high alcohol diet
In clinical practice, an RER > 1.00 can indicate:
- hyperventilation
- overfeeding
- acidosis
Once RER has been computed from gaseous exchange, the EE is calculated based on….
the caloric value of 1L of O2 and 1L of CO2, given various RERs
The amounts of ____ and ____ being oxidized in the production of these calories is also possible.
- CHO
- FAT
Why is the oxidation of protein ignored in the determination of the non-protein RQ?
because under ordinary circumstances the contribution of protein to energy metabolism is so small
____ rather than _____ basal or REE has been the practice among clinicians since 1925.
- estimating
- measuring
Estimations have been based on:
- body SA
- body weight
- calculations from regression equations that incorporate age, sex, weight, height
Estimates have been shown to correlate with measurements from ____ _____ and ____ ____ _____.
- indirect calorimetry
- doubly labeled water
Commonly used equations to estimate REE in healthy adults:
- Mifflin-St Jeor
- Harris-Benedict
Commonly used equation to estimate TEE in healthy, normal weight adults 19 years and older:
Dietary Reference Intakes (DRIs)