Energy Flashcards
Energy definition
Metabolic fuel needed for ALL bodily functions, provided from the macronutrients in our food
2 ways energy is measured
- Calorie
- Joule
Energy balance
Energy expenditure = Energy intake
Negative energy balance
Energy expenditure > Energy intake
Positive energy balance
Energy expenditure < Energy intake
Energy intake
Study of both the quantity of food eaten and its energy content
What is the energy per macronutrient for CARBOHYDRATES
4 kcal/g
What is the energy per macronutrient for PROTEIN
4 kcal/g
What is the energy per macronutrient for FAT
9 kcal/g
What is the energy per macronutrient for ALCOHOL
7 kcal/g
Basal Metabolic Rate definition
The amount of the energy required by the body at rest
Non-exercise thermogenesis definition
Energy used during day-to-day tasks
Exercise activity thermogenic definition
The energy used during exercise and for recovery from exercise
Total daily energy expenditure definition
All added together
Conditions of measurements of BMR
- After 12 hours of eating
- No vigorous exercise 24 hours prior
- Minimal emotional disturbance
- Awake
- Thermoneutrality
What are the 4 factors affecting BMR
- Body size
- Age
- Pregnancy/lactation
- Disease/trauma/treatment
Body size affecting BMR
More energy needed for bigger people
Age affecting BMR
More energy is early years (growth and activity)
Pregnancy affecting BMR
More energy required to produce and express breast milk
Disease affecting BMR
- Fever/stress etc. increases metabolic rate
- Medications may increase or decrease rate
2 ways to measure energy expenditure
- Direct calorimetry
- Indirect calorimetry
Direct calorimetry
- Strictly controlled conditions
- Extreme technical complexity
- High cost
- Changing temperature of the water direct equivalent to energy expenditure
Indirect calorimetry
- Measurement of heat production by assessing oxygen consumption and carbon dioxide production
- Knowledge of oxygen consumed, the heat production can be calculated
Douglas bag
- Estimation of energy expenditure
- Breathes via a mouthpiece and one way valve so that the expired gas is collected in a large bag over a certain period
- Volume is measured for oxygen and carbon dioxide content
Doubly labelled water
- Ingestion of “heavy” water that is isotopically labelled with deuterium and oxygen-18
- Urine sample collected for ~2 weeks
- Precise but expensive technique
Thermic Effect of Food (TEF)
Need to generate heat to maintain the constantly body temperature all macronutrients contribute towards heat production
Non-exercise activity thermogenesis
The amount of energy expended through non-exercise related movements
Exercise Activity Thermogenesis (EAT)
The amount of energy expended during exercise
How are DRVs set (2 ways)
- Energy expenditure measure
- Energy intake data from surveys
Caloric deficit fat LOSS
Energy in 2000 kcals – Energy out 2500 kcals
Caloric deficit fat GAIN
Energy in 2500 kcals – Energy out 2000 kcals
Fat mass and obesity related gene (FTO)
A cluster of single nucleotide polymorphisms (SNPs) in the first intron of the fat mass and obesity related (FTO) gene were the first common variants discovered to be associated with body mass
How to calculate energy expenditure
Henry equation
Physical activity ratio
- Energy use of physical activity
- A ratio of BMR
Physical activity level
- PAR x time spent in each activity over 24 hours
- Also, as a ratio of BMR
