Fasted commute

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531colin
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Re: Fasted commute

Postby 531colin » 15 Oct 2020, 5:57pm

PH wrote:I'm happy to learn more, but my understanding has been that the body has enough stored glycogen for the sort of effort described in the OP. Something like 2,000 calories?


And partially depleting that store would be expected to have an effect? ....or no effect?

Jdsk
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Re: Fasted commute

Postby Jdsk » 15 Oct 2020, 6:18pm

PH wrote:... the body has enough stored glycogen for the sort of effort described in the OP. Something like 2,000 calories?

About 400 g glycogen in muscle, about 100 g in liver. But you can't run it down to zero,
17 kJ/g of glycogen. (4 kcal/g.)

"Fundamentals of glycogen metabolism for coaches and athletes"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6019055/

...

This chapter has a neat table (30.3) comparing the various energy stores:
"Fuel Choice During Exercise Is Determined by Intensity and Duration of Activity"
https://www.ncbi.nlm.nih.gov/books/NBK22417/

Jonathan
Last edited by Jdsk on 15 Oct 2020, 6:22pm, edited 1 time in total.

Jdsk
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Re: Fasted commute

Postby Jdsk » 15 Oct 2020, 6:19pm

531colin wrote:
PH wrote:... the body has enough stored glycogen for the sort of effort described in the OP. Something like 2,000 calories?

And partially depleting that store would be expected to have an effect? ....or no effect?

It would have lots of effects... any particular ones of interest?

Jonathan

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531colin
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Re: Fasted commute

Postby 531colin » 15 Oct 2020, 6:33pm

Jdsk wrote:
531colin wrote:
PH wrote:... the body has enough stored glycogen for the sort of effort described in the OP. Something like 2,000 calories?

And partially depleting that store would be expected to have an effect? ....or no effect?

It would have lots of effects... any particular ones of interest?

Jonathan


As previously, really...I thought/read somewhere/ assumed....that (repeatedly) depleting glycogen stores by fasted exercising would facilitate fatty acid metabolism for energy.

Is there anything written on the subject where there is a reasonable degree of agreement between "experts" and which I could read and understand?

Jdsk
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Re: Fasted commute

Postby Jdsk » 15 Oct 2020, 6:38pm

531colin wrote:
Jdsk wrote:
531colin wrote:And partially depleting that store would be expected to have an effect? ....or no effect?

It would have lots of effects... any particular ones of interest?

As previously, really...I thought/read somewhere/ assumed....that (repeatedly) depleting glycogen stores by fasted exercising would facilitate fatty acid metabolism for energy.

Whenever you exercise for a fair bit you'll turn fatty acid oxidation on. But you're asking about a training effect... I don't know about that, but I wouldn't be surprised. NB local blood supply etc could also be affected so it wouldn't have to be a biochemical effect to allow higher rates of oxidation.

531colin wrote:Is there anything written on the subject where there is a reasonable degree of agreement between "experts" and which I could read and understand?

I'd start with the two sources linked above.

Jonathan

PS: You might not have meant it with the quotation marks but there really are experts on this stuff. : - )

PH
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Re: Fasted commute

Postby PH » 15 Oct 2020, 9:42pm

Jdsk wrote:
PH wrote:... the body has enough stored glycogen for the sort of effort described in the OP. Something like 2,000 calories?

About 400 g glycogen in muscle, about 100 g in liver. But you can't run it down to zero,
17 kJ/g of glycogen. (4 kcal/g.)

"Fundamentals of glycogen metabolism for coaches and athletes"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6019055/

...

This chapter has a neat table (30.3) comparing the various energy stores:
"Fuel Choice During Exercise Is Determined by Intensity and Duration of Activity"
https://www.ncbi.nlm.nih.gov/books/NBK22417/

Jonathan

Thanks for those, I've read them but am not sure I've got to grips with it, I'll maybe have another go. It's also hard to see how much of it relates to the OP. One of the papers says that after 2 hours intense exercise as athlete will be on the threshold of having depleted the muscle glycogen to a level that will effect performance. I don't know if the OP considers themselves as an athlete, I'm pretty sure the 10km commute isn't an intense 2 hours.
I used to have an active but only occasionally strenuous job, I'm pretty sure I would have used up more glycogen in the course of the mornings work than in the half hour ride there.

Jdsk
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Re: Fasted commute

Postby Jdsk » 15 Oct 2020, 9:43pm

PH wrote:It's also hard to see how much of it relates to the OP.

I wasn't restricting my answers to that...

; - )

Jonathan

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Re: Fasted commute

Postby PH » 15 Oct 2020, 9:45pm

Jdsk wrote:
PH wrote:It's also hard to see how much of it relates to the OP.

I wasn't restricting my answers to that...

; - )

Jonathan

OK - But those links are in a post with you quoting me making that point :wink:

ChrisP100
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Re: Fasted commute

Postby ChrisP100 » 16 Oct 2020, 9:18am

PH wrote:I don't know if the OP considers themselves as an athlete, I'm pretty sure the 10km commute isn't an intense 2 hours.
I used to have an active but only occasionally strenuous job, I'm pretty sure I would have used up more glycogen in the course of the mornings work than in the half hour ride there.

My job can be strenuous at times, but I'm mainly sat at a desk. I work between 2 offices, with 3 flights of stairs in between, and I'm probably up and down the stairs between 6 and 8 times a day.

I'm no athlete for sure, although I do have a resting heart rate of 51bpm which is excellent for my age. I don't hang around on my 10k ride in the morning, but certainly not flat out for the most part. The hill is most definitely the hardest part of my ride, and wind dependant my heart rate can be anywhere between 152 and 162 by the time I get to the top, so my body is certainly working hard, and my legs are burning. It steepens to 15% at the top where I'm averaging between 5 and 8mph.

Jamesh
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Re: Fasted commute

Postby Jamesh » 23 Oct 2020, 12:39pm

I've always done shorter training rides / runs 2h/1hr respectively fasted...

I think it trains the body to be more efficient and burns unwanted far that we seem to accumulate as we get older! I'm 43 btw. I see chaps riding to the cafe having a latte and cake and are probably gaining calories!!

.when it comes to longer rides.... I tend to eat something but not enough to replace all the energy I use. So a 100 mile 6hr ride I might eat a sandwich, KitKat chunky and few haribo.

When I run marathons 3hr pace, I tend to take 6 gels which I consume before water stations to stop me having a sticky mouth / hands for the next 5 miles!!

I don't know if I'm off the mark or not I looked into it about a decade ago when I got into running

Cheers James

Jdsk
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Re: Fasted commute

Postby Jdsk » 24 Oct 2020, 9:37am

Jamesh wrote:I think it trains the body to be more efficient and burns unwanted far that we seem to accumulate as we get older! I'm 43 btw. I see chaps riding to the cafe having a latte and cake and are probably gaining calories!!

If you don't eat as much later as you would have done before it will certainly decrease weight.

I'm not aware of any evidence that there's a training effect so that doing it repeatedly changes anything beyond each day's ride, but many physiological processes do have something like that.

Jonathan

Jamesh
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Re: Fasted commute

Postby Jamesh » 25 Oct 2020, 9:18pm

What do you think to this

https://www.cyclist.co.uk/in-depth/1199 ... to-fasting

Good Science or "expert opinion!"

Cheers James

Jdsk
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Re: Fasted commute

Postby Jdsk » 25 Oct 2020, 9:27pm

As written it's not good science and doesn't even cite its sources so that readers can find out more.

"Better mitochondrial health" is waffle.

But that doesn't mean that there isn't some good science behind it.

Jonathan

PS: I wonder if the the study on mitochondria is the same as the one discussed here:
https://news.harvard.edu/gazette/story/2017/11/intermittent-fasting-may-be-center-of-increasing-lifespan/
on... nematode worms.

mumbojumbo
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Re: Fasted commute

Postby mumbojumbo » 26 Oct 2020, 6:20am

The next meal could be your last.Always eat first,and if hungry after cycling grab a Mars or Jordans at work.I like to get up and listen to Farming Today to learn more about our gallant sons of the soil and the price of four row barley.

Jamesh
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Re: Fasted commute

Postby Jamesh » 26 Oct 2020, 7:16am

Jdsk wrote:As written it's not good science and doesn't even cite its sources so that readers can find out more.

"Better mitochondrial health" is waffle.

But that doesn't mean that there isn't some good science behind it.

Jonathan

PS: I wonder if the the study on mitochondria is the same as the one discussed here:
https://news.harvard.edu/gazette/story/2017/11/intermittent-fasting-may-be-center-of-increasing-lifespan/
on... nematode worms.


I thought so after properly reading it "expert opinion!"

Anyhow just a banana before my 20 mile ride.

Cheers James