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  • Glucose replacement



    Hey everyone! Being PB, we utilize fat to make glucose for energy. We also do short workouts so we don't burn our supply. My question is: if you do longer workouts and burn more glucose, what is the "Average" time it takes your body to turn fat into glucose to replace the glucose you just burned?


    I know it depends on the person, activity, etc... but is there a "round-about" time for the body to get back the glucose in the blood?


    Also, is anyone using "Endurox" or another type of post-workout (long workouts) recovery drink? It's about 52g of carbs but is designed for high-intensity or over 60 min workouts.


  • #2
    1



    I don't know the answer to the 1st part of your question although I would be interested in knowing that myself.


    As far as the 2nd part I use Prograde Workout. It's supposed to be a 2-scoop serving but I break it in half w/1 scoop pre & 1 scoop post. It's 32g carbs & 14g protein total but I don't worry too much about the 16g I'm getting post workout since it's replenishing what I lost and building muscles.


    By the way, you don't need to workout over 60 minutes for it to be intense. Try some Tabata thrusters or Tabata anything for that matter to get an "intense" workout! :-)

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    • #3
      1



      You can't make glucose from fat. You can get energy from fat, but it doesn't go through glucose as an intermediate.


      When glucose stores (glycogen) are low, you start burning triglycerides (fat) for energy. When a triglyceride molecule is "burned," it is broken down into one molecule of glycerol and 3 fatty acids. The glycerol and fatty acids are then converted to acetyl CoA, which enters the Krebs cycle and is used to generate ATP (energy!). ATP is the energy currency used by your cells to do work, such as muscle contraction.


      If you've already adapted to a low carb diet, your body is good at converting fat to energy, and your muscles will be happy to use fat instead of glucose. Therefore, you will consume your glycogen stores more slowly than someone who eats high carb. Once you've been on a low carb diet for a while, you're unlikely to wipe out your glycogen stores with anything less than truly extreme exercise.


      But what if you DO deplete your glycogen, or if you just need to top off your glycogen stores? Your body will obtain glucose to replenish your glycogen stores from one of three places: (1) carbs that you eat, (2) protein that you eat that is converted to glucose, or (3) protein that is scavenged from other body tissues.


      So the length of time it takes to replenish your glycogen stores is going to vary depending on how much glycogen you consumed, and what you eat after exertion.

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      • #4
        1



        Very informative post, Pikaia. So it is possible to lift weights on a depleted glycogen state? If you're adapted to it, that is.

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        • #5
          1



          Raphael, under what circumstances would your glycogen be completely depleted? Remember that when low carb adapted you use glycogen more slowly, because you&#39;ll be using fat for energy starting early in your workout.


          I suppose if you ran a marathon, you&#39;d probably deplete much of your glycogen stores. If you then tried to lift weights...well, it might not be pretty.


          Thinking about completely depleted glycogen has reminded me of a group of inherited diseases that screw up glycogen utilization. They&#39;re called glycogen storage diseases (GSD). These individuals can make glycogen, but they&#39;re lacking adequate function of one of the enzymes needed to metabolize glycogen. Gluconeogenesis may also be impaired. Sometimes the impairment affects all tissues, and sometimes it is specific to a particular tissue type, like muscle.


          Symptoms vary greatly depending on which GSD an individual has. But most types of GSD cause muscle cramps and weakness.


          I suspect you&#39;d have similar muscle symptoms if you tried to lift weights while completely glycogen depleted: your muscles would complain mightily and you&#39;d be too weak to accomplish any serious lifting.

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          • #6
            1



            Well I fast for 20 hours than lift weights for 1 hour... is that enough to deplete my glycogen stores? Just curious.

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            • #7
              1



              Raphael, during a 20 hour fast you&#39;ll burn almost zero glycogen...unless you&#39;re participating in higher intensity exercise during the fast. Remember, complete depletion of glycogen stores happens with activities like running above 85% of max HR for 2 hours straight. If you&#39;re just going through a normal day and fasting, it&#39;s almost exclusively fat you&#39;re burning.

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              • #8
                1



                Oh I thought that the body switched to burning fat only when glycogen is low.

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                • #9
                  1



                  @Raphael


                  Body switches to burning fat when insulin is low. It has nothing to do with Glycogen stores.


                  Liver is the biggest store of glycogen. It is used to stabilize blood glucose during fasting. Blood glucose is utilized by cells for energy while insulin is high. At all times Brain utilizes at least 25% of its energy from glucose. All this energy comes mostly from Liver. Muscles can also release some if they are over full.


                  Palmitic acid is used to prevent uptake of glucose (by inducing insulin resistance) during very low or zero carb diet, otherwise cells would consume all the available glucose in the blood, and you will get too low.


                  Mostly muscle glycogen is used for generating energy at a very high rate. This can be done only anaerobically. So you will be spending a lot of it during heavy lifting. It will depend on your workout, and you will know if you have run out of it. If you cannot complete your workout then you would have depleted it.


                  It cannot be depleted completely, but that is not important.

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                  • #10
                    1

                    [quote]

                    You can&#39;t make glucose from fat.
                    </blockquote>


                    What a load of rubbish.


                    Of course you can replenish glycogen stores by eating fat.


                    Triglyceride is a glyceride in which the glycerol is esterified with three fatty acids. It is the main constituent of animal fats. The glycerol component can be converted to glucose by the liver.

                    The "Seven Deadly Sins"

                    • Grains (wheat/rice/oats etc) . . . . . • Dairy (milk/yogurt/butter/cheese etc) . . . . .• Nightshades (peppers/tomato/eggplant etc)
                    • Tubers (potato/arrowroot etc) . . . • Modernly palatable (cashews/olives etc) . . . • Refined foods (salt/sugars etc )
                    • Legumes (soy/beans/peas etc)

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                    • #11
                      1



                      aside from chemistry stuff, i keep wondering why would anyone want to replenish glycogen stores during a workout - isn&#39;t it exactly what one works out for, i.e. to exert oneself (=deplete glycogen stores)


                      of course, if one is a professional athlete who gets paid for his/her performance that would make sense, but, to think of it, one doesn&#39;t work out just to work out and for the sake of working out, and refilling your "fuel tank" during excercise is useless and, i guess, counterproductive

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                      • #12
                        1



                        Tarlach, that happens only in the liver or kidney.


                        During a workout, it is true that you are undergoing gluconeogenesis and lipolysis at the same time. However, most of the fat you&#39;re burning is stored outside of the liver. During a workout, the majority of the glycerol formed from the breakdown of fat outside the liver doesn&#39;t enter gluconeogenesis. Instead it is taken up by muscle (or other) cells, converted to acetyl CoA, and finally enters the Krebs cycle.


                        In animal models, even in a fasted (partial glycogen depleted) state the liver can only take up about 25% of the glycerol found in the bloodstream. The rest is utilized by other body tissues. Again in animal models, inhibition of lipolysis does not significantly change the rate of glycogen depletion. The conclusion that can be drawn from this is that the products of lipolysis are not major players in synthesis of glucose for glycogen repletion.


                        I&#39;ll concede that it is biochemically possible. But let&#39;s talk about reality. The contribution of triglyceride metabolism to glycogen repletion is small compared to the others I listed (dietary carb, dietary protein, and protein catabolism).


                        Fat -> glucose -> glycogen just isn&#39;t a significant part of our metabolism.

                        Comment


                        • #13
                          1



                          @Pikaia


                          I don&#39;t agree that during workout most of the fat burnt is from the fat around the liver.


                          I have seen on me that I lost my skin fat while I was just doing workouts but following eating less eating 6 times a day.


                          I started to lose my abdominal fat only when I started low carb periods.


                          I think during workouts fat around skin gets burnt, and at all times when insulin is low, fat around liver will go first.


                          So the glycerol produced from fat breakdown will not convert to glucose, as it would need to get to the liver first.


                          Also I understand that glycerol to glucose conversion is not very common, and cannot be relied upon. The only real option is protein (whether dietary or muscular) to glucose conversion.

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                          • #14
                            1



                            Anand, I don&#39;t disagree with you. Maybe my wording was ambiguous. I wrote: "However, most of the fat you&#39;re burning is stored outside of the liver." By that I meant that it is NOT stored in/around the liver. It is distant to the liver, ie. subcutaneous fat or intramuscular fat.


                            But if what Tarlach says is happening, it can only happen in the liver or kidney, because only the liver or kidney can make glucose out of glycerol. Since we know that the majority of glycerol liberated from triglycerides doesn&#39;t end up in the liver or kidney, there&#39;s no way for it to be converted to glucose. We agree on that, right?

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                            • #15
                              1



                              I was thinking about this after visiting Charles Washington’s blog (http://blog.zeroinginonhealth.com/) and reading about his workout. He appears to have no problems whatsoever with rapidly-depleting/repleting glycogen stores.


                              The need to replenish muscle glycogen stores through dietary carbs might very well blown out of proportion.

                              “Every saint has a past and every sinner has a future.” -Oscar Wilde
                              "The power of accurate observation is commonly called cynicism by those who have not got it." -George Bernard Shaw
                              "The trouble with jogging is that the ice falls out of your glass." -Martin Mull

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