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Thread: Ketosis and Glycogen page

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    lcme's Avatar
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    Primal Fuel


    I have a pretty good understanding of all of these biochemical pathways on the molecular level. Where I come up short is in understanding how they interact.


    It is my understanding that in the initial few days of an LC/PB diet your body will resort to burning your liver glycogen stores (the muscle ones too?). My question is if/when does the body begin to replenish these stores when committing to a low carbohydrate nutrition plan.


    I guess my question essentially pertains to exercise as I feel very tired, because I am used to exercising in a range that requires carbohydrate fuel.


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    Molecular Grokologist's Avatar
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    You might be surprised how little research there is on fat adaptation, but I'll do my best to fill in the gaps with informed speculation.


    With low carbs following a high carb diet, the body will first attempt to use sugars from your glycogen. Your glycogen will gradually deplete. When your glycogen depletes entirely, you will enter ketosis.


    As you adapt to fat burning, your tissues will stop demanding sugar so urgently and will start to accept fat more readily. As a result, carbs over 100g (the amount demanded by the brain and a few other tissues) will begin to refill glycogen stores. Additionally, excess protein will be used to refill them.

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    Thanks MG. You and I seem to share a background in biochem, but I find the lack of data on how the body as a whole utilizes energy very shocking.


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    Ooer! I love all of this biochem lately. This forum is awesome for foodies and a lot of laughs but without the nerd stuff it is incomplete in my opinion.

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    I'm going through this same thing (I started another thread "how to fuel up..."). Very very tired after exercise.


    How long does it take to get through this adaptation period, and if we add more carbs to our diet, say increase by 75g making a total of 150 instead of 75g total, does this stall or prevent the adaptation to fat burning? It seems like I am re-filling my glycogen stores (but more slowly than my body wants), then depleting them again, feeling tired, refilling them, repeat. And like I said in my other thread, I'm concerned that when I'm exercising at high intensity and the glycogen stores are down, my body is turning to protein from my muscles rather than to fat as the next-best fuel source. That's what I've always read happens (albeit in a non-PB adapted body).

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    I have continued my same weight lifting routine since converting to PB a little over a month ago. The first few weeks were tough, I assume due to the drop in carbs.


    However, now, I feel great. I don't carb-up or do anything different before my workout. I did reduce my weight poundages by about 10% when I first changed to PB. However, I am making steady gains now. I feel like I am starting to gain more muscle, which does not make sense based on CW since I am getting an average of only 75g carbs per day.


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    @ Canarygirl


    Typically 2 weeks, but it takes some people longer. Drawing on protein from your muscles instead of fat just isn't what your body prefers to do. It does the minimum necessary to keep your blood glucose steady (drawing from dietary protein first where it can), then it draws from junk/unnecessary/low priority proteins, THEN it goes for important stuff like muscles. That is, at least, if you don't have a ton of catabolic hormones running around messing this sequence up.


    Once you fat adapt, your body is going to find reasons to draw on glycogen less and less, so it becomes even less of an issue.


    150g carbs may (I'm not sure anybody's actually shown this to be the case) be on the high end of fat adaptation, but think of it this way: what's your primary calorie source? That's what your body is going to prefer to burn.

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    @ Carnarygirl In direct response to the muscle breakdown question.


    The body does require certain amino acids (protein) for gluconeogenesis (making glucose itself). As long as your dietary protein is high enough your body is not going to need to break down muscle.


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    Yeah I always hear about ketosis being this horrible state of the body consuming itself for energy but that makes no sense from an evolutionary perspective. Free amino acids would be utilized before actually breaking down the muscle. Muscle is important to kill stuff! And I don't think lack of protein is an issue, as many issues with protein intake of more than 30% are too much excess wherein the kidneys are tired ridding all of it from the body.

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