Bioenergetics - energy expenditure

what is energy?

ability or capacity to do work or to cause damage, measured in joules

what is a calorie?

amount of energy needed to raise 1mL water by 1 degrees

what is a kilocalorie

amount of energy needed to raise 1L water by 1 degrees

how to get balanced weight in energy balance

energy in equals energy out

how to get weight gain in energy balance

energy in is greater than energy out

how to get weight loss in energy balance

energy out is greater than energy in

what is equation of energy intake

energy expended(heat and work) + energy stored = energy intake

what factors make up total daily energy expenditure(TDEE)?

1. resting metabolic rate(RMR)/ basal metabolic rate (BMR)

2. thermal effect of food(TEF)/diet induced thermogenesis(DIT)

3. Thermal effect of activity

example of RMR/BMR

breathing

what is TEF/DIT used for?

used to digest food and absorb nutrients aswell as for metabolism and storage - makes up 6-10% EE

what is TEA used for?

energy used by any movement, most variable as changes depending on a persons activity levels

what is basal metabolic rate/resting metabolic rate

energy cost of maintaining normal function

RMR exceeds BMR

what is BMR/RMR influenced by

age

sex

body size

nutritional and hormonal status

activity levels

how is BMR/RMR measured

measured upon waking in a fasted state

estimated using 3 equations:

1. Harris-Benedict (2019) if age, sex and stature are known

2. Schofield (1985) if mass, age and sex is known

3. Henry(2005) if mass,age,sex and stature is known

how does the thermic effect of food vary?

varies with different macronutrients:

1. loss of ingested calories from protein consumption = 27.5% - high protein diet burns more calories

2. carbohydrate consumption = 7%

3. fat consumption = 2.5%

what is thermic effect of activity

how all types of physical activity affect energy expenditure

definition of physical activity

body movement produced by skeletal muscle contraction

definition of energy expenditure

result of physical activity and reflects the net transfer of energy required to support muscle contraction

which factor of TDEE makes up most energy expenditure?

RMR/BMR is the most and TEA is the least

what are the 4 ways to measure energy expenditure

1. objective measurement

2. self-report measurement

3. direct measurement

4. indirect measurement

how to measure energy expenditure with direct measurement

direct calorimetry - method measuring amount energy expended by monitoring the rate a person loses heat from the body using a whole room calorimeter

what is the gold standard technique to assess energy expenditure?

Doubly labelled water

what is doubly labelled water

water where both hydrogen and oxygen have been partly or completely replaced with an uncommon isotope

how to measure energy expenditure indirectly

indirect calorimetry - Douglas bags and breath by breath systems are used to measure pulmonary gas exchanges

how is energy expenditure measured by self report

use questionnaires, physical activity diary or 24 hour recall

pros of self report methods

manage large number participants at low cost, measure variety dimensions and suitable for lots people

cons of self report method

recall challenges for some, inaccuracies due to bias

what are the 2 ways to measure physical activity induced energy expenditure

1. physical activity level (PAL)

2. metabolic equivalent of task (MET)

what is the physical activity level (PAL)

the ratio of total energy expenditure to resting metabolic rate

equation for physical activity level

total energy expenditure = BMR x PAL

what is the metabolic equivalent of task (MET)

comprehensive list of activities to classify energy cost of physical activity

equation for metabolic equivalent of task

energy expenditure = MET x duration

equation for total daily energy expenditure

TDEE = BMR/RMR + thermic effect of activity + thermic effect of food 

what is energy balance

relationship between energy in and energy out

what percentage of energy expenditure is from RMR/BMR

60-80%

what percentage of energy expenditure is from thermal effect of food

6-10%

what percent of energy expenditure is from thermal effect of activity 

varies but smallest