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Keto and cycling

Old 04-27-21, 10:53 AM
  #51  
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Originally Posted by guachi View Post
I wish I could find the scientific study but it was a study about where energy comes from during exercise. Like many exercise studies, it used cyclists on a cycling ergometer. The cyclists exercised at different intensity levels and then measurements were taken. At rest all energy needs were met via free fatty acids and blood glucose. As aerobic intensity increased glycogen and fat usage (I can't remember the exact type of fat but whatever muscular fat is called) both increased as muscles were now having to work. Both kept increasing until a certain point (it was 65% but I can't remember 65% of what - V02 max, lactate threshold, max heart rate, FTP - but it was at a moderate intensity) and after that fat usage actually decreased and carbohydrate usage shot up like a rocket.

So if you were actually interested in burning lots of fat it seems the best way to do it would be to ride at a low-moderate pace as well as get that low-moderate pace as high as possible by, at times, actually consuming carbohydrates and working hard to increase your fitness.
That's what we used to believe when only gas exchange ratio was used to determine fat burning. Turns out it's more complicated that that. There's an old saw, "fat burns in a carbohydrate flame," which turns out to be true. You have to have carbs to burn fat. It also turns out that for the well-trained athlete, as you go harder, fat burning doesn't drop off like they used to think. In fact at very high intensities it actually increases. Turns out that the way to lose weight is just like we always thought: exercise hard and don't eat too much. Each of these links has a slightly different take on the subject:

https://www.jackkunkel.com/blog/why-.../#.YIg_trVKiUl
https://www.answers.com/Q/What_does_..._flame%27_mean
https://www.trainingpeaks.com/blog/w...carbohydrates/
https://medium.com/fastfitnesstips/m...s-4ea49fd23a85


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Old 04-27-21, 11:52 AM
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Originally Posted by rubiksoval View Post
The deal is your body needs carbohydrates to ride at any type of intensity.

If your goal is to plod around as slowly as possible for random amounts of time, low carb/keto may suffice.
well not sure what you think plodding is it under 200watts? I cant eat carbs my body hates them and they cause a lot of problems they actually slow me down. So I pretty much run on protein only with veggies a few times a week. even fat does not really do much energy wise for me. on a good day I can average 180 watts for over a hour on a really good day 200 watts. I have ridden 225 miles in a week and I do at least 20 miles a day. I have bonked as I am still learning how many calories I need to eat. Plus protein is slow energy so I have to plan ahead. it is a big learning curve and my body does not go into keitosis even with 2 weeks of no carbs at all.
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Old 04-27-21, 05:56 PM
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That chart supports what I wrote. At about 65% fat usage drops and carbohydrate usage shoots up like a rocket. The study I read only tested three points: 65%, something less than 65%, and something greater than 65% (IIRC, 80%).

The Training Peaks article references work done by Len Kravitz. He has a blog I stumbled across several years ago that has good articles about exercise and links to other works. Worth a look. https://www.unm.edu/~lkravitz/Pages/articles.html

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Old 04-27-21, 07:04 PM
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Originally Posted by fooferdoggie View Post
well not sure what you think plodding is it under 200watts?
Because it's not a substantial amount of power that requires a substantial amount of energy. Pretty simple.
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Old 04-27-21, 07:07 PM
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Originally Posted by guachi View Post
That chart supports what I wrote. At about 65% fat usage drops and carbohydrate usage shoots up like a rocket. The study I read only tested three points: 65%, something less than 65%, and something greater than 65% (IIRC, 80%).

The Training Peaks article references work done by Len Kravitz. He has a blog I stumbled across several years ago that has good articles about exercise and links to other works. Worth a look. https://www.unm.edu/~lkravitz/Pages/articles.html
This is the usual graph one sees, which is derived from exhaled gasses:



The problem is that there's a fallacy involved with using exhaled gas to derive energy sources used. It was explained in one of my links, above. You can see the very large difference in fat oxidation.
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