Module 2: FAT Recommendations for Athletes Flashcards
Why fats are important
- Fuel for contracting muscles
- Absorption of fat-soluble vitamins
- Cell- membrane structure
- formation of hormones and immunity
When is fat the primary fuel with intensity?
at low – moderate exercise intensities typically under ~60-65% VO2max
* As exercise intensity increases above ~60-65% VO2max there is a shift in energy substrate utilization wherein fat oxidation decreased and carbohydrate oxidation increases.
When is fat primary fuel source with duration
As exercise duration increases the contribution of fat to total energy expenditure increases.
Fat metabolism during exercise
FA metabolism during exercise yields more ATP than CHO metabolism on its own, but O2 is needed, which puts stress on the CV system.
* high-intensity exercise is limited by CHO availability; glucose and glycogen
training and dietary strategies in an attempt to identify mechanisms through which fat metabolism could be manipulated to spare glycogen
- Medium Chain Triglyceride (MCT) feedings
- Fat Loading
- Supplements such as caffeine
Characteristics of MCTs
medium chain triglycerides
* Normally present in our diet in very small quantities
* Few naturally occurring food sources
* Usually synthesized from coconut oil
* 8 to 10 carbon molecule
* Liquid at room temperature
Theory behind MCTs to be used in sparing glycogen
MCT’s are quickly absorbed. After digestion, MCTs travel to the liver where they are immediately used for energy. They are also do not have to be carried by chylomicrons and are transported very rapidly to the muscle. So theoretically, this means that MCT’s could help to spare glycogen in athletes by providing a rapidly available substrate for aerobic metabolism.
What is a rich source of MCTs?
coconut oil
Evidence of coconut oil on sport performance
- Coconut oil increases total cholesterol by about 15 points, LDL by 10 points, and HDL by 4 points.
- No significant effect on body weight, waist circumference, or body fat percentage.
- Coconut oil contains as many calories and total fat as other fat sources, about 120 calories and 14 grams of fat per tablespoon (15 mL).
The American Heart Association has issued a scientific advisory cautioning the public to limit their intake of coconut oil.
Evidence for MCTs in sport
- Ingestion of MCT (30 g dose) does not spare muscle glycogen contributes less than 10% to energy generation.
- MCT, even when oxidized well, does not add much energy.
- Ingestion of larger amounts of MCT results in dose dependent,
gastrointestinal distress.
high-fat, low- carbohydrate diets to enhance sport performance by forcing the body to oxidize fats at a higher rate, which would potentially spare glycogen and enhance endurance.
Fat loading
Fat loading
high-fat, low- carbohydrate diets to enhance sport performance by forcing the body to oxidize fats at a higher rate, which would potentially spare glycogen and enhance endurance.
Evidence for fat loading diets
To date, the evidence to support this hypothesis has not offered strong support for fat loading/high fat diets for athletes.
* In general high fat/low CHO diets appear to reduce rather than enhance metabolic flexibility by reducing carbohydrate availability and capacity to use carbohydrate effectively as an exercise substrate.
* Athletes should not attempt fat loading or a high fat/low carb eating as this approach has the potential to sacrifice their ability to undertake high- quality training or high-intensity efforts during competition
Caffeine effect on fat utilization during sport
Caffeine is a pharmacologic ergogenic aid that has been shown to be able to:
* Increase Time to Exhaustion (TTE)
* Alter the perception of effort as a result of it’s impact on the CNS
* Alter levels of key enzymes in skeletal muscle to down regulate CHO breakdown
* Enhance fat oxidation and decreasing CHO utilization
How might caffeine enhance sport performance?
Benefits most likely involve caffeine’s capacity to bind to adenosine receptors
* Adenosine receptors help regulate many physiological, neurological and immunological processes which may lead to alterations to the perception of effort or fatigue, as well as direct effects on the circulatory system and skeletal muscle.
hydroxycut dose
4 capsules per day with water in conjunction with a calorie-
reduced diet and a regular exercise program.
* The only reason this supplement might work is because of the reduced calories and exercise, and losing fluid from the high intake of caffeine; not the supplement itself
