Dietary Fat and Exercise Flashcards
Do fats have a high or low TEF? What does this mean?
low TEF - low energy cost for digestion/storage
Do fats have an efficient storage?
yes, stored with very little water (unlike carbs)
What fat-soluble vitamins are absorbed with fats?
ADEK
What is the energy of 1g of fat?
9kcal/gram
What are the 4 storage forms of fats? Which storage form stores the most energy?
most energy stored in adipose tissue triglycerides
1-serum free fatty acids (7)
2- serum triglycerides (75)
3- muscle triglycerides (2,500)
4- adipose tissue triglycerides (80,000)
What is ketosis?
When body switches to using fat as a dominant fuel source.
Often after 12 hrs fasting - breaking down adipose tissue triglycerides.
What are lipids?
What is their composition?
dietary fats, insoluble in water
composed of carbon, hydrogen, and oxygen
What are triglycerides composed of?
glycerol backbone, and 3 FA attached to each glycerol
What are the types of lipids?
TG, phospholipids, cholesterol
What is the AMDR for fat?
For 1-3yrs, 4-18yrs, and 19+yrs?
1-3yrs: 30-40%
4-18yrs: 25-35%
19+yrs: 20-35%
What is the recommended dietary allowance (RDA), adequate intake (AI) or upper limits (UL) for total fat?
No RDA, AI, or UL
except for infants AI: 30g/day
6-12M AI: 31g/day
What is the recommendations for fat intake (types / degrees of saturation)?
saturated fatty acids (10%)
minimize trans fat intake
max 7-10% from saturated and trans fats (combined)
monounsaturated FA (MUFA) - 10%
polyunsaturated FA (PUFA) - 10%
Is there a benefit to a low fat diet for athletes?
no, no benefit for this. consuming <20%kcal from fat is not beneficial, neither is a high fat diet.
What is esterification? When is this process favoured?
formation of triglycerides: combination of an acid and alcohol (glycerol) ester
process of formation favoured after eating a meal
What is fat lypolysis or hydrolysis?
When is this process favoured?
the breakdown of TGs to yield energy from FAs and glycerol
process favoured during exercise, low cal dieting, low energy availability, fasting/starvation, decreased insulin concentrations; increased GH, cortisol and catecholamines (fight or flight response); when body is cold
When the body is cold is lypolysis or TG formation favoured?
favours lipolysis
the 3 hydrolysis reactions for lipolysis are catalyzed by what enzyme?
hormone-sensitive lipase
What are the 2 major fates of fat mobilization?
re-esterification to TG (storage of fat)
exit from the fat cell (as FFA or attached to albumin)
What is beta-oxidation?
mobilization of fatty acids into acetyl-CoA
Then acetyl-CoA is processed via Krebs cycle and ETC system to produce ATP
At rest, what % of energy is supplied by metabolism of fats?
~60% (when consuming mixed diet)
What happens as plasma FFAs are being used up?
FFA are being mobilized from adipose tissue
what % of FFA released get “re-esterfied” back into triglycerides at rest?
70% - build back up into TG and stored in adipose tissue
what are 2 major sources of ATP for exercise?
CHO and fat
FFA - mainly LCFA
FAs are used by muscle during exercise and may be derived from:
from plasma triglycerides, plasma FFA, fatty acids from intramuscular TGs
Is there a big supply of plasma FFAs?
no, they are in very short supply and must be supplied by adipose TG stores
What is the role of Hormone Sensitive Lipase (HSL)?
How does consumption of CHO during exercise impact HSL activity?
catabolizes glycerol and FFA
consumption of CHO during exercise reduces HSL activity (has fat-sparing effect)
How does aerobic training impact fat oxidation?
What does the amount of change from training depend on?
increases fat oxidation
amount of increase dependent on intensity, duration of activity, dietary state, physical conditioning (training status)
Explain the “crossover effect”.
the point of exercise intensity at which the body starts to rely more on CHO than fat as the dominant fuel
lipolysis of TG to FFA in adipose, transport to blood, oxidizing in muscle mitochondria is too slow to keep pace with metabolic demand
higher intensity - more carbs used, lower fat usage
Does the crossover effect change if we supply more fat during exercise?
no, still doesn’t change that graph
What happens to the release of FFA from adipose tissue at higher intensities of exercise? Why?
decreases
reduced adipose tissue blood flow - decreased delivery of FFA to contracting muscle tissue
What happens when additional FFA is provided during exercise at ~80%VO2max?
FFA oxidation was increased but not fully restored.
mechanisms within the muscle must limit FA oxidation at high intensities
What % of the FFAs will go through re-esterification during exercise?
only 25% are built back up and increase in FFA delivery to muscle cells
How does epinephrine secreted during exercise affect fat metabolism?
stimulates breakdown of adipose TG and release of FFA into blood for transport to the muscle for oxidation
How does muscle contraction impact fat metabolism?
activates transporters, thus increasing FFA uptake into muscle cells
intramuscular lipases are stimulated to catabolize muscle TG to FFA; then FFAs can enter the mitochondria and be degraded to acetyl-CoA
At exercise intensities <25%VO2max, fat supplies __% of energy.
80%
At exercise intensity beyond __%, CHO dominates
above 65%
What are the gender differences in fat oxidation?
females may be able to oxidize more fat during exercise at 65-75%VO2max (higher intensities)
What does the body do as exercise intensity/duration increases (>90min)?
muscle glycogen stores decrease, the body switches to fat oxidation
FFAs may produce ~__% of energy in the latter stages of extended exercise at lower intensities (ex. ultramarathons)?
90%
Does a trained individual or sedentary individual oxidize more fat?
trained
How does increased training impact fat metabolism? What does it improve?
BF to muscle –> more FFA
intramuscular TG -> increased content and use
sensitivity to epinephrine –> more FFA
increase in number and size of mitochondria
FFA transport across mitochondrial membrane
oxidative enzyme activity
What unique ability do trained athletes have as exercise intensity increases?
ability to oxidize triglycerides when exercise intensity increases; allowing more fat to be used as energy during exercise (glycogen sparing)
What happens when you adapt to a low CHO, high FAT diet?
Are high fat diets beneficial for perofrmance?
you can increase the oxidation of fats
- potential for glycogen sparing
no benefit for performance so far
may be a few scenarios where LCHF diets are of benefit or at least not detrimental for sports performance
What is the downside to LCHF diet for performance?
no benefit really - costs exercise economy (using more oxygen to get same performance)
Goal is to have _ servings of fatty fish per week.
2 Canada’s food guide servings
include a small amount of ___________ fats in your diet daily.
unsaturated
(limit saturated fat, trans fat, animal fat)
Why might you encourage an athlete involved in high intensity intermittent sport to limit fat intake pre-competition?
1- tolerance
2- feeling of fullness
3- gastric emptying
4- focus on carbs
5- no performance benefit to excess fat
Fish contain what essential fat?
What are the recommendations for males and females?
Omega-3 fatty acids
F: 1.1g/day
M: 1.6g/day
What is the benefit of omega-3 fatty acids?
- direct blood vessels to dilate
- encourage blood to stay fluid
- reduce inflammation response seen in heart disease
- become part of cell structure making them healthier
Are there different types of Omega-3 fatty acids?
yes, 4 types, combination of them is needed
What are some good sources of Omega-3 fatty acids?
rainbow trout, salmon, herring, ground flaxseed, canola oil, walnuts
What is the AI for Omega-6 fatty acids in males and females?
F: 12g/day
M: 17g/day
What types of Omega-6 fatty acids are there?
Linoleic acid, and arachidonic acid
What are Omega-6 food sources?
meats, poultry, eggs, nuts/seeds, plant-based oils (canola, sunflower)
What are concerns for Omega-6 fatty acids in excessive amounts?
excessive amounts in the diet can contribute to inflammation and result in heart disease, cancer, asthma, arthritis, etc.
What is the goal balance between Omega-6 and Omega-3?
4:1 ratio
What are Omega-9 fatty acids? What food sources do they come from?
monounsaturated fats (oleic acids)
food sources: canola oil, sunflower oil, olive and nut oils, almonds
Canola and sunflower oil are high in monounsaturated fats, low in saturated fats, FREE of trans fat
Can Omega-9 be produced by the body?
yes, but also beneficial when consumed as part of diet
What is the benefit of Omega-9?
helps reduce the risk of CVD and stroke, increase HDL, and decrease LDL
Should athletes follow the same dietary guidelines regarding fat intake as the general population?
yes
sometimes pre-comp - decreased fat intake to increase carb stores, or when changes in body comp required (reduced to 20% of total kcal)
