Is a high fat diet beneficial for athletes? Flashcards
describe the basic structure of a triglyceride
glycerol backbone and 3 fatty acids, joined to it via ester bonds
what does the 18:1n-9 indicate about the structure of oleic acid
has a total of 18 carbon atoms
has 1 double bond
the double bond is 9 carbons from the n terminus
why are some fatty acids classed as essential fatty acids?
because the body doesn’t have the enzymes it needs to synthesise them and therefore they have to be consumed in the diet
during which types of exercise are fats used to contribute to energy provision
light and moderate intensity
as intensity increased more of the energy is provided by glycogen utalisation
how does the utalisation of fat as a fuel source change over the duration of prolonged exercise
proportion contributed by fat increases due to the depletion of muscle glycogen
in relation to fat metabolism, what benefit has been seen with endurance training
following intervention, percentage of total energy contributed by triglycerides increased
therefore the utalisation of glycogen decreased
describe the control mechanism leading to a switch from glucose to fat utalisation during exercise
glucose in the blood = increased insulin
insulin suppresses the activity of hormone sensitive lipase which causes a reduction in the release of triglycerides from adipose tissue
therefore there are less FA in the blood
fall in glucose and therefore a fall in insulin would reverse this
has short term fat loading been shown to be beneficial to endurance exercise performance
no
high carb vs high fat for 3 days
high carb = longer TTE
greater difference at low vs high temperature because here it was glycogen depletion which was the limiting factor rather than thermal stress
high carb still better in high temp because it reduces perceived exertion
what were the findings of a study into longer term fat loading (15 days)
increased fat oxidation during submaximal exercise and simulanteous decrease in carb oxidation
but no difference in 40km TT performance
(no benefit but no harm)
what is the theory behind the idea of dietry periodisation
having a high fat diet normally to get the benefits of increased utalisation of fats and therefore less glycogen depletion
then few days before competition do intensive carb loading to increase the depleted glycogen stores
what does the evidence regarding the idea of dietary periodisation show
muscle glycogen was depeleted with a high fat diet but one day of carb feeding was able to restore it
high fat diet decreased glycogen utalisation during exercise test and increased fat oxidation
but was no significant difference in TT performance
what is the effect of a high fat diet on response to training (vs high carb diet)
impairs response to training
high carb had a greater improvement in TTE
RPE was similar between two groups before training but much higher for high fat group after
what was the effect of a high fat diet on cycle road race performance (vs high carb)
both had 1 day carb loading before race
no difference in performance time
high fat had worse performance when sprinting
what conclusions can be made from the evidence regarding high fat diets
are unlikely to improve performance for most athletes
may be beneficial for a small number of athletes, possibly some ultra-endurance athletes
high fat diets increase fat use during exercise
training + high fat diet = reduced high intensity performance
high fat diet is unlikely to optomise performance for most athletes
accoriding to the paper by Burke et al, what is the threshold level of carbohydrate intake, above which no further increase in glycogen synthesis will occur
1.2g/kg/hr
