Lecture 5 - Fats

Question 1

benefits of fat

Answer 1

• fat provides the essential fatty acids
• dietary fats also serve to enhance satiety and help satisfy total energy needs
• certains foods also provide omega-3
• athletes should be cautious of eating too much fat t avoid potential for inflammation particularly from saturated fats, trans fatty acids and omega 6 fatty acids
• fat stores around organs can act as insulators

Question 2

fat storage in athletes vs non athletes

Answer 2

we can store an obscene amount of fat, stores are available in adipose tissue and muscle fibres
- average storeage in adipose tissue ranges between 50,000 and 100,000 calories
- in addition, athletes store approximately 2000 to 3000 calories of lipids inside muscle tissue

Question 3

how/when are fatty acids oxidized during exercise?

Answer 3

they’re oxidized in the mitochondria of skeletal muscle

Question 4

where are the fatty acids (that we oxidize during exercise) derived from

Answer 4

• adipose tissue triaglycerol (TAG) is broken down by hormone-sesitive lipase (HSL)
• intramuscular triacylglycerol (IMTG) is broken down by HSL
• plasma triaclyglycerols are broken down by endothelial lipoprotein lipase
• glycerol from TAG is transported to the liver where it serves as a gluconeogenic substrate to form new glucose

Question 5

IMTG

Answer 5

Intramuscular triacylglycerol
- usually located adjacent to the mitochondria as lipid droplets, is an important energy source
- droplets are closer to mitochondria in trained individuals so it’s easier to oxidize them as they don’t need to travel far and a greater proportion are oxidized

Question 6

_______ is the predominant fuel at rest and for light exercise

Answer 6

FAT

Question 7

relate fat oxidation rates to exercise duration and intensity

Answer 7

when exercise is initiated, the rate of lipolysis and the rate of FAs release from adipose tissue increases
- during moderate-intensity exercise
1. lipolysis increases approximately three fold
2 BF to the adipose tissue is doubled and the rate of reesterification is halved
- BF to skeletal muscles increases dramatically and the delivery of FAs to the muscle increases

Question 8

which ratios of high/low fat and carb diets increases/decreases fat oxidation

Answer 8

high carb, low fat diet REDUCES fat oxidization whereas a high fat low car diet increases fat oxidation

Question 9

how are carbs vs fat metabolism regulated

Answer 9

• carbs are highly regulated but fats aren’t as much. The rate of fat utilization during exercise is mainly influence by the level of fat avilibility and rate of carb utilzation (increase carbs increases insulin which decreases lypolysis)

Question 10

albumin

Answer 10

the blood protein albumin is the primary lipid transporter from storage to working muscles

Question 11

relate fasting and exercise performance

Answer 11

• fasting increases lipolysis and plasma FA availability, resulting in an increased oxidation of FAs at rest and during exercise
• performance is not imparied at low intensities but it is at higher intensities (50-100%VO2Max)
• this decreased performance is not reversible by carb ingestion during exercise

Question 12

adaptations of a chronic high fat diet

Answer 12

• they have been shown to induce metabolic adaptions and to increase fat oxidation and exercise performance in rates but the situation appears to be different in humans
• these adaptations include an increased activity of oxidative enzyme
• despite increased fat oxidization during exercise, performance is unaffected in humans

Question 13

how do high fat diets impair high intensity exercise

Answer 13

• in well trained individuals, long term high fat diets do not seem to improve endurance performance compared with high carb diets
• several studies indicate that the performance of bouts of high intensity exercise at intervals during prolonged steady state exercise are impaired by high fat diets
• essentially this mean that for most sports, a high fat diet is not suitable or desirable

Question 14

long-chain FAs vs medium chain FAs during exercise

Answer 14

Long chain FAs
- absorption is slow
- benefits are questionable
Medium chain FAs
- absorption is faster
- benefits are questionable, possible gastric upset
AVOID FATS DURING EXERCISE

Question 15

what percentage of your total calories ingested should be fats?

Answer 15

• 20-35% should be fats
• there is no scientific information suggesting that more than 25% of total calories from fat is generally better for athletes
• athletes with high energy needs can consume up to 35%