5 ms·

>Yes, but that works on the idea that providing no glucose to the body will make it switch to fat instead. So it's not really diet "controlling" which fuel sour

>Yes, but that works on the idea that providing no glucose to the body will make it switch to fat instead. So it's not really diet "controlling" which fuel source to use I think there is just a difference in the use of "controlling" here. Fat/Glucose will always be used jointly as energy, but the idea is to "control" which is the primary fuel source. A Ketogenic diet or ketosis is part of that, still giving you a fair reading I can understand how you conclude that is not "control", though I would argue it is because I am controlling my fuel source, but to your point I am not eating whatever I want (carb/sugar heavy diet) and controlling my primary fuel source like a light switch. Separate and apart from the diet, there are other things you can do to "control" or "train" your body to burn fat as the primary fuel source. Again keto is a large part of it, but lets assume I am in ketosis and about to go for one of my runs...in short, aerobic or anaerobic. Is my body going to go for the fat or is it going to go for the available glucose which is the preferred energy source for anaerobic exercise? Also, in anaerobic exercise the muscles produce lactic acid as a by product and as anaerobic exercise can only be maintained for a short period of time, when its over and the body is recovering the lactic acid goes to the liver and is converted into glucose, of course that raises the blood glucose level which in turn may encourage the body to use as the primary fuel source. Keeping my run aerobic I am "controlling" the primary fuel source and burning fat, both in the short term (same run) and long term (over periods of time) I am training my body to be pushed harder and harder while maintaining my aerobic threshold increases.

stefan_ 8y ago
Deriving energy from fat is strictly less oxygen efficient than from glycogen; oxygen supply of course being the main limiter of aerobic endurance. This is why as you increase intensity towards VO2max the balance of fat versus glycogen use shifts dramatically in favor of glycogen. So training in a glycogen depleted state (back then we called this bonking) is bad news if you want to increase your aerobic threshold, since the kind of training that has been shown most effective in causing the required adaptations involves repeated maximal efforts. The only training effect you can hope for is nudging your body towards using more fat at lower levels of exertion, thereby saving valuable glycogen. This isn't very relevant for most running events which are typically done at a consistently high VO2max percentage, but beneficial for say cycling races where you have low intensity (riding in the slipstream on the flat) mixed with very high intensity (up a steep grade).
- deleted 8y ago
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- will_brown 8y ago
  >So training in a glycogen depleted state (back then we called this bonking) is bad news if you want to increase your aerobic threshold These is a difference between burning glucose as the primary fuel source, depleting it, and bonking vs using fat as the primary fuel source to begin with (there is no bonking). But basically glucose store empty pretty quickly and if not refueled the body shuts down to conserve the limited glucose for the brain because that is it’s primary fuel source (the body shut down is the bonking). When in keotsis, the burning of fat produces a by product, ketones, which is a different source of fuel for the brain. So when in ketosis when burning fat as the primary fuel source (which is essentially limitless compared to glucose) there is no bonk because 1. You don’t run out of fat (like you would glucose), and 2. As you burn fat you produce ketones to fuel the brain (which isn’t happening when burning glucose as the primary fuel). For example my last marathon I ran in ketosis I did with only water and electrolytes (no fuel), I cant do that if I’m not in ketosis. Your point about being able to more efficiently increase the aerobic threshold while using glucose sounds right.

stefan_ 8y ago

Deriving energy from fat is strictly less oxygen efficient than from glycogen; oxygen supply of course being the main limiter of aerobic endurance. This is why as you increase intensity towards VO2max the balance of fat versus glycogen use shifts dramatically in favor of glycogen. So training in a glycogen depleted state (back then we called this bonking) is bad news if you want to increase your aerobic threshold, since the kind of training that has been shown most effective in causing the required adaptations involves repeated maximal efforts. The only training effect you can hope for is nudging your body towards using more fat at lower levels of exertion, thereby saving valuable glycogen. This isn't very relevant for most running events which are typically done at a consistently high VO2max percentage, but beneficial for say cycling races where you have low intensity (riding in the slipstream on the flat) mixed with very high intensity (up a steep grade).

deleted 8y ago
[deleted]
will_brown 8y ago
>So training in a glycogen depleted state (back then we called this bonking) is bad news if you want to increase your aerobic threshold These is a difference between burning glucose as the primary fuel source, depleting it, and bonking vs using fat as the primary fuel source to begin with (there is no bonking). But basically glucose store empty pretty quickly and if not refueled the body shuts down to conserve the limited glucose for the brain because that is it’s primary fuel source (the body shut down is the bonking). When in keotsis, the burning of fat produces a by product, ketones, which is a different source of fuel for the brain. So when in ketosis when burning fat as the primary fuel source (which is essentially limitless compared to glucose) there is no bonk because 1. You don’t run out of fat (like you would glucose), and 2. As you burn fat you produce ketones to fuel the brain (which isn’t happening when burning glucose as the primary fuel). For example my last marathon I ran in ketosis I did with only water and electrolytes (no fuel), I cant do that if I’m not in ketosis. Your point about being able to more efficiently increase the aerobic threshold while using glucose sounds right.