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  1. #21
    dkJames's Avatar
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    He did not say that fat was "better" at producing CO2 but that fat oxidation yields more CO2 by simply looking at the number of carbon atoms and chemical equation above. I don't see a logical problem here.

  2. #22
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    Quote Originally Posted by dkJames View Post
    He did not say that fat was "better" at producing CO2 but that fat oxidation yields more CO2 by simply looking at the number of carbon atoms and chemical equation above. I don't see a logical problem here.
    I read this: "If all we're after is increasing CO2 output, oxidizing dietary fat is the way to go." as exactly what I said. It's incomplete and misleading.

    RQ is the respiratory quotient. His equation represents carbon, oxygen, and hydrogen metabolism. But, for specific macronutrients, it breaks down like this.

    c6h12o6 + 6 O2 -> 6 CO2 + 6 H2O the gas exchanged is equal so... rq = 6 co2 / 6 o2 = 1.0

    If we take his 16 co2 it would leave fat with an RQ of 0.696 round up to 0.7

    c16h32o2 + 23 o2-> 16 co2 + 16 h20 16 co2 / 23 o2 = 0.696

    Fat also oxidizes much slower due to this fact.
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  3. #23
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    Quote Originally Posted by Derpamix View Post
    I read this: "If all we're after is increasing CO2 output, oxidizing dietary fat is the way to go." as exactly what I said. It's incomplete and misleading.

    RQ is the respiratory quotient. His equation represents carbon, oxygen, and hydrogen metabolism. But, for specific macronutrients, it breaks down like this.

    c6h12o6 + 6 O2 -> 6 CO2 + 6 H2O the gas exchanged is equal so... rq = 6 co2 / 6 o2 = 1.0

    If we take his 16 co2 it would leave fat with an RQ of 0.696 round up to 0.7

    c16h32o2 + 23 o2-> 16 co2 + 16 h20 16 co2 / 23 o2 = 0.696

    Fat also oxidizes much slower due to this fact.
    Yes, that is what is measured when people are on ketogenic diets: around 0.7. On highly glycemic, you get close to 1. So your numbers are consistent with the measurements.

  4. #24
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    Quote Originally Posted by Derpamix View Post
    I read this: "If all we're after is increasing CO2 output, oxidizing dietary fat is the way to go." as exactly what I said. It's incomplete and misleading.

    RQ is the respiratory quotient. His equation represents carbon, oxygen, and hydrogen metabolism. But, for specific macronutrients, it breaks down like this.

    c6h12o6 + 6 O2 -> 6 CO2 + 6 H2O the gas exchanged is equal so... rq = 6 co2 / 6 o2 = 1.0

    If we take his 16 co2 it would leave fat with an RQ of 0.696 round up to 0.7

    c16h32o2 + 23 o2-> 16 co2 + 16 h20 16 co2 / 23 o2 = 0.696

    Fat also oxidizes much slower due to this fact.
    So ... respiratory quotient is a ratio, as you show above, CO2 to O2. And you are correct, an RQ of about 0.7 represents fat oxidation, whereas a respiratory quotient of 1.0 represents CHO oxidation. And you are also correct in your observation that 0.7 is less than 1.0. The wheels fall off when you fail to (or refuse to?) recognize that 6CO2 molecules is almost three times less than 16CO2. The fact that the oxidation of palmitate ( in this case ) takes more exogenous oxygen is irrelevant and ultimately a result of stoichiometry, not "my equation."

    Again, I stand by my original assertion ... "if all you care about is CO2 production", all you need to do is manipulate the carbon chain length of whatever it is that you are oxidizing. If you want to increase it, oxidize something with lots of carbon. If you want to decrease it, oxidize something with less carbon. The carbon is, after all, the source of the C in the CO2. Please take the time to digest the fact that by the very definition of RQ, since you are actually comparing carbon dioxide production to oxygen consumption, you obviously care about both, and that violates my stated condition that "all you care about is CO2 production."

    This was in direct response to Choco's unsubstantiated statements regarding CO2 and "impaired mitochondrial respiration" which, as you can now see by crunching the numbers yourself, is pure drivel. The only way that I can see for that to be incomplete and misleading is for one to go and strip away all the context when quoting me.

    As far as the rates of oxidation of CHO relative to fats is concerned ... the oxidation equations as presented generally relate to pure combustion. That energy is given off as heat, whereas the biochemical pathways that actually generate energy for cells harness the energy of oxidation to phosphorylate ADP, and they do so in a very controlled manner. You can't go around releasing combustion level energy within a cell and expect that cell to remain viable.

    While I'm not sure about this, I suspect that your comments relating to fats oxidizing more slowly than carbohydrates stem from confusion regarding substrate level vs. oxidative phosphorylation, which relates to how cells generate ATP. In the case of substrate level phosphorylation, this pathway is only available to glucose and it is very fast, and rather inefficient. For every molecule of glucose that undergoes substrate level phosphorylation, you very quickly generate two ATP molecules and two pyruvate molecules. The chief advantages here are that this is a very quick process, it occurs in the cellular cytoplasm, and requires zero oxygen. The drawback, to reiterate, is the inefficiency of the process vis a vis ATP production.

    Oxidative phosphorylation, on the other hand, is orders of magnitude more efficient at ATP production, yielding about 30 ATP molecules per glucose, and roughly three times that amount for long chain fatty acids. Oxidative phosphorylation is quite slow relative to substrate level phosphorylation, it takes place in mitochondria ( which means your cells must have them, and not all your cells do ), and as the name plainly suggests, it requires oxygen, hence the oxidative label.

    Both fats and glucose can enter the oxidative phosphorylation pathway, glucose via its pyruvate metabolite, and fats via beta oxidation, and they both provide intermediate metabolites for the TCA cycle and the electron transport chain. So, apart from the relatively few chemical reactions that initiate oxidative phosphorylation, the remainder of the reactions involved are indistinguishable for fats and carbohydrates.

    Now, it is possible that I have misunderstood you and that you were actually intending to enter into a discussion with me over the kinetics of the enzymes that catalyze the initial distinct pathways of fats and CHO, but I considered that a fairly low probability outcome. Nevertheless, since that probability is not zero, if that is the discussion you want to have, I'll leave it up to you to come up with the initial data regarding the relative kinetics of the enzymes that catalyze the various oxidative phosporylation pathways.

    -PK
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  5. #25
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    I always wonder during these conversations... how many people involved in them have ever been Keto while also being regularly tested for things like CO2 levels?

    Oh. Me.
    ...because I take a medication that can mess up my CO2 levels. (My neurologist says being Keto has nothing to do with it.)

    Yeah.
    Always mid-high normal range.

    I've also had my cortisol tested because of long term medication use and chronic disease... normal (despite "Keto").
    Though my doc says keto is also no reason to worry about that either.


    Always the same scare tactics. It's ridiculous.
    Some people are so biased it's painful.
    It's almost as bad as Choco's "only cold water fish are fatty" argument.
    “You have your way. I have my way. As for the right way, the correct way, and the only way, it does not exist.”
    ~Friedrich Nietzsche
    And that's why I'm here eating HFLC Primal/Paleo.


  6. #26
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    Quote Originally Posted by cori93437 View Post
    It's almost as bad as Choco's "only cold water fish are fatty" argument.
    But is the fat rendered? That is the question.

    But seriously, thanks, PK for another well written and researched post.

  7. #27
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    The reason why fats produce more ATP coincides with the fact it oxidizes much slower. Fats have to be transported from fat cell tissue to metabolize in form of vesicles, which are taken up through endocytosis and degraded into fatty acids, then finally have to be converted into acetyl CoA before entering beta oxidation. Also, the fact fat contains an enormous amount of carbons and have to have already circulating oxygen in the cells in order to couple further slows this process. Also, fat oxidation produces huge amounts of water, which can burden the cells and respiratory system and cause lactic acid build up to take the place of the missing oxygen for energy, which shortens the ATP produced.

    Have you ever left a banana out and watched how fast it browns?

    The pathway for glucose -> pyruvate -> acetyl CoA is much simpler and preferred as principal source for acetyl CoA and mitochondrial function. For example: with each cycle, a fatty acid is shortened by two carbons while oxidized and its energy captured by the reduced energy carriers nadh and fadh2. At the end of the four reactions, one acetyl CoA 2 carbon unit is released from the end of the fatty acid, going through another round of beta oxidation, continuing to shorten even chain fatty acids until they are entirely converted to acetyl CoA. Eventually you're left with an odd number of carbons in the acyl chain, which cannot enter another round of beta oxidation.

    This is typically why we store fat as energy, as it's much more dense, oxidizes slower, and is too complex and burdening to use as a main source of energy.

    I'll also assume you're talking about short chained fatty acids, as very long chain fatty acids cannot be used by the mitochondria and produce no ATP(peroxisome beta oxidation)
    Last edited by Derpamix; 06-01-2013 at 09:03 PM.
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  8. #28
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    Quote Originally Posted by cori93437 View Post
    I always wonder during these conversations... how many people involved in them have ever been Keto while also being regularly tested for things like CO2 levels?

    Oh. Me.
    ...because I take a medication that can mess up my CO2 levels. (My neurologist says being Keto has nothing to do with it.)

    Yeah.
    Always mid-high normal range.

    I've also had my cortisol tested because of long term medication use and chronic disease... normal (despite "Keto").
    Though my doc says keto is also no reason to worry about that either.


    Always the same scare tactics. It's ridiculous.
    Some people are so biased it's painful.
    It's almost as bad as Choco's "only cold water fish are fatty" argument.
    I think that, beta oxidation of short chain fatty acids is sufficient enough to support metabolism, co2, and the mitochondria, it's just never the preferred choice. It's also that, most people have far too much circulating PUFA, which not only compromises this, but is vastly harmful, as liberating free fatty acids dictates. It causes problems with fat metabolism as well as glucose.

    Also, too many variables, no one person's anecdotal experience amounts to anything, your problem is probably just what was said above, and a compromised glucose metabolism. But, whatever supports your health and works for you, you're the only one who really knows. I know, for me personally, VLC was absolutely destructive to my health in all ways.
    Last edited by Derpamix; 06-01-2013 at 09:20 PM.
    nihil

  9. #29
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    Oh, well I guess if bananas turn brown when left out in hot weather, that means VLC is a bad diet.

    Cori, why didn't anyone tell us about this sooner? <passes the bread to Cori>

    But seriously Derp. Nobody is pro-PUFA around here so you can quit fighting that strawman.

    And, "This is typically why we store fat as energy, as it's much more dense, oxidizes slower, and is too complex and burdening to use as a main source of energy." (/Derpquote)

    Could easily be re-written as, "We store fat as energy as it's much more dense, oxidizes slower, and is therefor the perfect fuel to use as a main energy source while reserving glucose for infrequent short burst activities such as running away from a saber toothed tiger."

  10. #30
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    Quote Originally Posted by Paleobird View Post
    Oh, well I guess if bananas turn brown when left out in hot weather, that means VLC is a bad diet.

    Cori, why didn't anyone tell us about this sooner? <passes the bread to Cori>

    But seriously Derp. Nobody is pro-PUFA around here so you can quit fighting that strawman.

    And, "This is typically why we store fat as energy, as it's much more dense, oxidizes slower, and is too complex and burdening to use as a main source of energy." (/Derpquote)

    Could easily be re-written as, "We store fat as energy as it's much more dense, oxidizes slower, and is therefor the perfect fuel to use as a main energy source while reserving glucose for infrequent short burst activities such as running away from a saber toothed tiger."
    What are you talking about? -_- Bananas brown because they oxidize faster as referenced in my equation above. It has nothing to do with VLC. And bread is already oxidized. It was just about the equation and compositions.

    Seriously, why are you cherry picking useless abstracts when I'm not even addressing you?
    nihil

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