Energy Balance & substrate metabolism Flashcards
(16 cards)
What is energy balance
- Balance of energy in & out
- Positive energy balance when intake is longer than expenditure, meaning you put on weight
- Negative expand more than you intake : lose weight
What are the energy balance components
- Fat: ~9 kcal/g
- Carbohydrates: ~4 kcal/g
- Protein: ~4 kcal/g
- Ethanol: ~7 kcal/g
How do you measure energy expenditure
-Resting metabolic rate- energy needed to stay alive
State the 3 methods of measuring energy expenditure
- direct & indirect calorimetry
- Doubly Labelled Water Method
- Wearable devices & commercial trackers
What is indirect & indirect calorimetry
Direct: Measures heat production.
Indirect: Estimates energy expenditure via oxygen consumption and CO2 production.
Strength of calorimetry
- Accurate measurement of energy expenditure
- Real-time data
- Assessment of macronutrient oxidation
- Non-invasive
4 Limitations of calorimetry
- Measurement requires controlled conditions
- Limited subjects compliance and cooperation
- Not suitable for continuous measurement in free-living conditions
- Can be expensive
What is doubly-labelled water method
Measures CO2 production over time to estimate daily energy expenditure
3 Strength of Doubly labelled water method
- Free living conditions
- Non-invasive
- Long-term measurements
Weakness of doubly labelled water method
- Expensive
- Doesn’t provide data on specific sources of energy expenditure
How do you measure substrate metabolism
- Infuse a labelled glucose into a vein and then they ingest another form of carb and then sample blood and breath at various points
- Using the tracer methods- we can measure how much of the carb is coming from the drink vs what was already in the body
How do you measure liver glycogen
Magnetic resonance spectroscopy
- This method is very expensive
6 Factors effecting substrate metabolism during exercise
- Intensity and duration of exercise
- Nutritional status
- Training status
- Sex
- Mode of exercise
- Temperature and altitude
How do low, moderate & high exercise intensities effect the fuel used
- Low intensity: More fat oxidation.
- Moderate intensity: Balanced mix of carbohydrates and fats.
- High intensity: Predominantly carbohydrates.
How does exercise duration effect substrate use
- Short-duration: Glycogen is primary fuel.
- Long-duration: Increased reliance on fat as glycogen depletes.
What are the 5 limits of fat oxidation during high intensities exercise
o Insufficient stimulation of fat breakdown.
o Lactate accumulation inhibiting fat use.
o Reduced blood flow to adipose tissue.
o Transport limitations at the muscle level.
o Mitochondrial fatty acid transport bottlenecks.
