Fat Flashcards
Discuss Whitley et al (1998)??
Looked at the effects of high fat meals on substrate oxidation and performance during moderate exercise.
- showed no difference in time to complete 10km time trial between fast/ high fat (30F/50C/14P) and high carb (3F/215C/26p)
- also showed no difference in NEFA and RER
Discuss Rowlands & Hopkins (2002)?
Showed a high fat diet increases fat oxidation and FFA vs the high CHO group
But no clear performance differences between the groups following a 50km TT
What did Starling et al (1997) find?? In detail.
Looked at the metabolic effects of short term high fat diets.
2h exercise @65%vo2 max followed by 24h refeeding with either High CHO ( 83%C5%F12%P) or high FAT (16% CHO, 68% F, 16% P)
Showed RER significantly higher for Hi-CHO.
Muscle TG sig ⬇️24h post ride for hi CHO, sig ⬆️24h for hi fat compared to hi CHO
For muscle glycogen, both decreased sig post race, but sig more 24h post ride for Hi CHO compared to Hi fat
Hi FAT was worse than HI CHO at 1600kj time trial
Discuss Zhender et al (2006)??
Looked at short term dietary fat over feeding
- showed 20km TT to be unaffected with a short term high fat, high CHO diet
Concluded when CHO dietary intake is maintained,short term increases in dietary fat can augment muscle lipid and maintain muscle glycogen
This doesn’t affect - whole body substrate oxidation, muscle glycogen use, time trial performance after a 3h pre load
Burke et al (2000) looked at high FAT-CHO restoration and found what??
Gave either a high fat for days 1-5, high CHO day 6, TT day 7.
Or high CHO diet days 1-6, TT day 7
Results showed fat adaptation at day 6 sig decreased muscle glycogen.
Non significant trend for fat adaptation to be quicker over performance trial.
Also affected oxidation significantly.
What did Havemann et al (2006) find??
Looked at high FAT-CHO restoration and high intensity exercise performance.
Showed a trend for HCD-CHO to be quicker on time trial than HFD-CHO. Also significantly less power output for HFD-CHO over 1km sprint compared to HCD-CHO
Stellingwerf et al (2006) looked at high CHO compared to a far-adapted group, what did they find??
Showed PDH activity was significantly higher In the high CHO group, following a 1 minute sprint @150%PPO, also significantly higher at 20 min post.
Poor PDH means impaired conversion of pyruvate to acetyl - CoA
Discuss the key Lambert et al (1994) paper?? When looking at longer term fat adaptation
Had 5 trained cyclists adapt for 2 weeks at either high CHO (70%) or high fat (70%)
Showed no differences in peak power output between high fat or high CHO.
During high intensity ex, time to exhaustion was ~50% longer for H-CHO but this was not significant perhaps due to small N
During mod intensity, time to exh was significantly longer for H fat, and RER sig higher for H-CHO.
What are some criticisms of the Lambert et al (1994) paper??
A bizarre testing protocol , high variability in the small N(type 2 error occurring) and low external validity (time to exh < time trial)
What’s the definition of a keto diet (don’t have source)
<50g CHO/day , fat intakes >80% energy
~15% or 1.5g/kg/d protein (not >25%)
- ensure sufficient electrolytes
- at least 2-3 weeks for keto - adaptation
Volek et al (2015) wanted to rethink fat as a fuel for endurance ex, what did they find??
Fatigue is due to reduced CHO availability and the inability to use alternative lipid sources .
A keto-adaptation ensures a stable fuel source for exercising muscle and the brain in the face of CHO availability
See notes for manipulation checks.
Results showed that 6 fold differences in long term dietary CHO (20 months) 82gvs684g - showed that low CHO is associated with a robust capacity to ⬆️fat oxidation during exercise while mAintaining normal muscle glycogen
Unfortunately this failed to translate to any performance changes but cross sessional design poses individual differences
Discuss Phinney et al (1983)
Looked at 5 trained cyclists that had 4 weeks on a LCD(<20g CHO/day) and exercise to exhaustion @62-64% VO2 max
This 4 week diet did not impair aerobic performance
During maximaL work, the RER was much lower in the keto diet , with a decreased ability to use CHO (⬇️EKD4)
Stated that this may limit anaerobic work with limited CHO.
However, high variance did occur, one subject increased by 100mins on time to exhaustion.
What did Phinney (2004) state?
Stated anaerobic performance is limited by low muscle glycogen, and strongly discourages its use under most competitive athletic situations
Discuss the comments made by Burke and Kiens (2006) and Burke (2015)?
BK - stated that it was the nail in the coffin for fat adaptation in athletic performance
Burke (2015) states there may be a few scenarios where LCHF diets are of benefit, or at least not detrimental for sports performance
Discuss the key study by Burke (2017) in elite race walkers
The three diets were - HCHO (60-65%CHO15-20%PRO20%F)
PCHO - same as above just periodised around training some high some low etc.
LCHF - 75-80% F 15-20% P, <50g/day CHO (keto from Volek and Phinney (2012))
3 week adaptation to a LCHF diet during a period of intensified training.
LCHF diet had markedly increases fat oxidation rates over a range of intensities - but, this results in a reduced running economy(⬆️o2 for a given demand) at real life velocities .
In contrast to HCHO or PCHO, adaptation to a LCHF diet impairs performance in elite endurance athletes despite a sig improvement in peak aerobic capacity.
