Advanced Nutrition and Metabolism

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Energy Expenditure
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Total Energy expenditure (EE) composed of

REE/BMR - resting energy expenditure/basal metabolic rate

TEF - the thermic effect of food

EE of physical activity



Basal metabolic rate (BMR)/Resting energy


it represents ____

represents the rate at which the body expends energy to sustain basic life processes such as respiration, blood circulation, heartbeat,renal function, and energy need to stay awake.


Basal metabolic rate (BMR)/Resting energy


generate __% of total EE

~60% of total EE


How can we measure BMR/REE?

determined when he/she is in a postabsorptive state (no food intake for 12 hours), is lying down, completely relaxed (motionless), neutral temperature of the room.


With aging lean mass (fat-free mass) ___

and BMR ___

decrease, decrease


Changes in BMR can occur when ___

whenever the proportions of body tissue change in relation to one another.

*total body weight 5%-6% attribute to brain, liver,

heart, kidneys; total body weight of muscles 30-40%

*metabolic activity of these organ tissues accounts for about 60% of basal oxygen consumption, whereas muscles mass accounts for only 25%.


A second component of EE is TEF.

TEF represents the increase in energy expenditure

- the thermic effect of food

- represent the increase in EE associated with body's processing of food due to: digestion, absorption, transport, metabolism, storage of energy from digested food.


Lipid increases EE more than carbohydrates



protein in foods has the greatest thermic effect, increasing EE 20% to 30%.

Proteins increase EE more than carbohydrates or fat.


A common value ascribed to the thermic effect of food is ____% when a mixed diet is consumed.

The value most commonly used for the thermic effect of food is 10% of the caloric value of a mixed diet consumed within 24 hours.


When TEF metabolism reaches maximum?

The rise in metabolism reaches maximum after 1 hour after eating


Third component of EE is energy expenditure of physical activity

it depends on/

Most variable component, also the only component that that is easily altered.

estimated at ~30% (20% - 40%)of EE, but it depends on intensity,duration, frequency of activity, body mass of the person and their efficiency of performing the activity


energy expenditure of physical activity estimated __% of EE



Oxygen consumption and thus energy expenditure can remain ___ for a short time period after the exercise activity has stopped.

remain elevated


Forth component of EE is Thermoregulation

what it is?

change in metabolism that occurs when body works to maintain temperature

takes energy to both heat and cool the body


Methods to Assess Energy Expenditure

Direct calorimetry

Indirect calorimetry


What is direct calorimetry?

card image

measure the dissipation (dispersion) of heat from the body


What is indirect calorimetry?

measures consumption of O2 and the expiration of carbon dioxide.


How can we measure indirect calorimetry?

what is RQ and what it represents?

The amount of Energy expended can be calculated from the ratio of the carbon dioxide expired to the oxygen inhaled. This ratio is known as respiratory quotient RQ.

RQ provide a meaningful information with respect to both EE and the biological substrate ( carbs or fat) being oxidized.




RQ=1 is for glucose

RQ=1 suggests that Carbohydrate is being oxidized, bc the amount of O2 required for the combustion of glucose equals the amount CO2 produced




RQ <1 for fat because fat is much less oxidized fuel source (fewer O2 molecules).


What is an approximate RQ for protein?

Estimation is more complex because metabolic oxidation of amino acids requires removing the N and some oxygen and carbon as Urea.estimate the amount of protein metabolized

estimate the amount of protein metabolized by the amount of N excreted in urine

RQ for protein = 0.8


RQ for fat, protein and carbohydrates

RQ = 1 Glucose

RQ = 0.7 Fat

RQ = 0.8 Protein


How to estimate RQ for proteins?

estimate the amount of protein metabolized by the amount of N excreted in urine


What can RQ estimate mean?

the RQ can be used to estimate how much CHO and lipid are being used


3rd method to assess energy expenditure is

Doubly labeled water

Stable isotopes of water 2H2 or 18O

At a specified later time, measure the amount of each isotope remaining.

  • disappearance of 18O represents the disappearance of body water (H2O) and the production rate of CO2
  • disappearance of 2H represents the disappearance of body water (H2O) only

Disappearance of 2H2 isotope represents

the disappearance of body water (H2O)

*only 2H2 can only be excreted as H2O.


Difference between the disappearance rate of 18O and 2H2 corresponds to the production rate of ____

production rate of CO2


How can we calculate production rate of CO2?

Difference between the disappearance rate of 18O and 2H2


How can we calculate O2 consumption?

Is it always valid?

To access O2 consumption, a food quotient (FQ) is calculated from diet records kept throughout the testing period.

This is valid only when there is no body weight change

To maintain body weight FQ = RQ


What is FQ?

Food quotient

calculated to access O2 consumption in doubly labeled water method.


What is main source of error for FQ?

main source of error is usually in the food records.


How can we calculate energy expenditure from doubly labeled water?

calculate the energy expenditure from the CO2 production and the O2 consumption derived from the FQ.


4th method to estimate energy expenditure

Derived formulas

formulas based on weight, height, gender and age for BMR

ex: Harris-Benedict equation (BMR is predicted in separate equations for men and women)


How to calculate BMR?

BMR can be estimated from body weight

• e.g. BMR = W^0.75 x 70 kcal/day

uses W measured in kg raised to the power of 0.75 and * by 70


Energy requirements depend on

  • depends on age, growth, gender
  • depends on physiological state – e.g.pregnancy, lactation, stress, fever, growth, fasting, malnutrition
  • physical activity influences
  • environmental conditions influence

What is EER?

Based on data on total daily EE measured by doubly labeled water method, equation for estimation of energy requirements was developed.

EER (estimated energy requirement) used in DRI are based on equations that include weight, height, gender, age and physical activity


Explain oxidative and substrate level phosphorylation –what are they, how are they different and what is their importance in metabolism. Give an example of substrate level phosphorylation.

oxidative phosphorylation = electron transport chain, major supplier of E from lipids and amino acids.


Substrate level Phosphorylation

Substrate-level phosphorylation is directly phosphorylating ADP with a phosphate and energy provided from a coupled reaction. SLP will only occur if there is a reaction that releases sufficient energy to allow the direct phosphorylation of ADP.

ex: phosphoenolpyruvate, 1,3-bisphosphoglycerate, creatine phosphate


Oxidative phosphorylation

Oxidative phosphorylation is when ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons. That process generates an electrochemical gradient, which is required to power the ATP synthase.


Explain (in general) how energy is transferred to ATP in the electron transport chain, using the chemiosmotic theory.

card image

This process, in which energy from a proton gradient is used to make ATP, is called chemiosmosis.

According to the chemiosmotic theory, the flow of protons into the matrix drives ATP production.


Explain how salicylic acid interrupts oxidative phosphorylation.

High doses of aspirin can increase body temperature by uncoupling the proton gradient.

The diffusion of the protonated ( acid) form of salicylic through the mictochondrial inner membrane and the release of its protons in the matrix.

The process reduces the proton concentration gradient across the membrane. This slow the passage of protons through ATPase channels and interferes with synthesis.


what is UCP?


UCP - uncoupling protein

UCPs are transmembrane proteins that decrease the proton gradient generated in oxidative phosphorylation. They do this by increasing the permeability of the inner mitochondrial membrane, allowing protons that have been pumped into the intermembrane space to return to the mitochondrial matrix.

ex: thermogenin found in mt of brown adipose tissue


Understand what thermogenin is, its importance and be able to explain how it works.

Uncoupling protein (UCP, thermogenin)
• found in brown adipose tissue (has more mitochondria)
• increases non-shivering thermogenesis


Describe where energy comes from under conditions of low physical activity, short-term high activity and long term activity.

Extreme: ATP-CP

Very high: ATP from carbohydrates(anaerobic)

High: ATP from carbohydrates( aerobic)

Moderate: ATP from fat (aerobic)


Explain the difference between aerobic and anaerobic
metabolism, and in which parts of metabolism each are involved.

Aerobic metabolism
1. TCA and ETC
2. limited by amount of O2 available
3. increased glycogen stores improve ability to exercise
4. fat also used - epinehrine secreted during exercise
increases activity of hormone sensitive lipase

Anaerobic metabolism(cori cyble)