Fuelling with Fat

Question 1

How is fat stored and utilized in sport?

Answer 1

Adipocyte
- TAGs - liplysis -> Glycerol to liver
- TAGs -> FFA to muscle and liver

Liver
- gluconeogenesis to ATP (Glucose) to mucles

Muscle
- Beta-oxidation
- intramuscular triglyceride

Question 2

Purpose of fat for athletes

Answer 2

insulation
Regulates hormone
Absorb vitamins
Protect organs
Energy provision

Question 3

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What is the theory of fat as an energy source for performance?

Answer 3

Provide higher yield energy source (9kcal/g)
Virtually endless storage potential
Reduce dependence on muscle glycogen during competition
* “Glycogen sparing”
Reduce dependence on CHO refueling during an event
Impacts enzymes involved in ATP generation (e.g., GLUT- 4, pyruvate dehydrogenase complex)

Question 4

CHO are the superior fueling source

Answer 4

CHO aerobic ATP production is ~7% more efficient than from fat
CHO metabolism is made for rapid delivery of ATP
Meets energy demands above 60-65% VO2 max
Can be used for anaerobic and aerobic ATP production

Focus should be on individualization & periodized fueling

Question 5

Why do we use high fat instead of high protein?

Answer 5

1. Increased kidney stress
2. Protein contributes low overall ATP via gluconeogenesis

Question 6

Ketogenic high fat diet

Answer 6

Diet criteria:
* Alter macronutrient concentrations to rely on fat (80-90% energy)
* 50g CHO per day
* Produces ketone bodies (ATP source via ketogenesis)
* VLKD (<20g CHO per day)

Question 7

Evidence of ketogenic high fat diet

Answer 7

5 well-trained cyclists (n=2 studies)
* 28 days of a severely carbohydrate-restricted (<20 g/day), isoenergetic

Findings
* Resting muscle glycogen stores were not depleted (reduced to 45%)
* Muscle glycogen depletion seen in type 1 fibers with 4x reduction in contribution to fuel use
* Blood glucose as fuel reduced 3x
* Gluconeogenic contributions from glycerol, lactate, pyruvate, and amino acids preventing hypoglycemia during exercise
* Lipid oxidation was increased
* Attenuation of respiratory quotient [RQ] value at VO2 max

Question 8

Non-ketogenic high fat diet (low carb high fat or LCHF diet)

Answer 8

Dietary criteria
* >60% fat intake (energy)
* <25% CHO intake (energy)
Goal
* Increase IMTG
* Reduce muscle glycogen
* Adaptations to ‘re-tool’ the muscle to alter fuel utilization patterns during exercise

Question 9

CHO re-fueling

Answer 9

Dietary criteria
* Short-term adaptation to an LCHF
* Glycogen restoration (‘carbohydrate loading’)
* 1–3 days of a carbohydrate-rich diet with or without additional CHO intake pre- and during subsequent exercise
Goal
* Increases in fat & CHO availability
* Increase fat & CHO utilization in exercise

Question 10

Caveats from evidence

Answer 10

• small sample size
• diversity in dietary protocols
• diversity in training protcol