Dispelling some exercise myths around glycogen and fat burning
Replies
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ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.EvgeniZyntx wrote: »ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
A little Googling found numbers that you mention, based on a 1994 study of endurance athletes studied after an overnight fast.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
Think of the burn rate needed to run through approximately 500 grams of carbohydrate in 30 minutes and you will see what nonsense that is.
Think of how far runners can go before they "hit the wall" or how long a cyclist goes before they "bonk". And how awful it feels (crushing and sudden fatigue, mental confusion such as forgetting to put your feet down when you stop pedalling! Yep done that.).
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
Agreed, it's ridiculous to talk about "running out of glycogen" without mentioning intensity. Light exercise is basically glycogen neutral. High intensity work (RER 1, preferentially CHO fuelled) will reduce global stores to about 20% in one hr in the trained athlete.
What does the bolded above actually mean? Exercising for less than 30 minutes now suddenly decreases muscle mass?ericGold15 wrote: »In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
First off, great post @rankinsect
Now, on to my derailment...
Does recent diet have any impact on this conversation? i.e. training fasted vs fed? Or is the idea of fasted training somewhat of a misnomer?
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
Anecdotal experience suggests it is so, but some of that may be mental.0 -
[*] Non-aerobic glycolysis last 45-150 seconds. Type II, or fast-twitch muscles, are the locus for glycolysis using stored muscle glycogen.
[*] The aerobic system, known as the Kerbs Cycle, provides most of the energy for effort of 3 minutes or longer. Type I, slow-twitching muscle, in conjunction with Type IIa, provides the mechanical work. For fuel, this system relies on fat at lower intensities progressing to carbohydrate as intensity increases.
[*] The phosphagen system is used during maximal effort which only have enough supply of energy for 10 seconds. Re-phosphorylation of ADP from phosphocreatine stores provides enough for about 25 seconds total. (Structured training utilizing this pathway is HIIT not to be confused by the garbage floating around recently).
[/list]
Just so we don't confuse @rainbowbow, when we say that we use the phosphagen system and then non-aerobic glycolysis for an additional 45-90 seconds, what he is describing is what happends when you go from a complete resting state into aerobic exercise and the various stages that occur to prepare your body to meet the abrupt increased energy demands.
So your body is not geared to provide the ATP necessary to use glycoysis and Krebs Cycle and ETC right away. Too many steps have to occur to supply this energy. So there are intermediate steps that the body can use to supply you energy from when you are standing on the starting line waiting for the gun to go off and then *BOOM* you start running pretty hard.
When you are at complete rest, your body is in a somewhat homeostatious state. As soon as you start running, your muscle cells rely immediately on extra ATP that is stored. Enough to supply you with enough ATP for about 3 seconds of contraction. Just enough time to allow the creatine phosphogen system to start supplying ATP (which acts very quickly). But the phophogen system only has enough resources in the muscle cell to supply about 10 seconds worth of ATP. While this is going on, glycolysis is kick started so by the time the phosphogen system runs out of resources, glycoylysis can begin supplying enough ATP. All of the systems described do not require oxygen to make ATP. So they are anaerobic (or non-aerobic) in nature. While this is going on, the body begins to quicken the heart rate (to pump more blood) so that more oxygen can be delivered to the muscle cells. Within 90 seconds from the moment you started running, there is now an increased amount of oxygen being delivered to your muscle cells so that Krebs Cycle and ETC can do their thing. The ratio to burn glucose verses fatty acids are increased until things get settled and you then begin to burn more fatty acids than glucose (assuming your intensity level allows for this).
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First off, great post @rankinsect
Now, on to my derailment...
Does recent diet have any impact on this conversation? i.e. training faster vs fed? Or is the idea of fasted training somewhat of a misnomer?
Example, are "depleted glycogen stores" more likely to happen more quickly when training 16 hours after your last meal as compared to 3 hours? Lets assume fairly high intensity cardio for 60-90 minutes.
Anecdotal experience suggests it is so, but some of that may be mental.
Diet can have a huge impact on all of this. That is why I carb load before my marathons. I have a post on this forum somewhere where I discuss carb loading, but you can actually store [temporarily] more glycogen than your body normally stores under certain conditions.
You mention running fasted. I do this sometimes. I actually do this a lot.
When you run fasted, you actually speed up the process when your body starts to exhaust glycogen. So if you run at a lowered intensity, your body is forced to make more use of fatty acids. Do this enough, then your body becomes more efficient at breaking down and using fatty acids. The harmones that are used in this process, your body learns to make more of it. So when you are running fully carbed up, there are more harmones in the body to break down and use fatty acids. So this influences the ratio of glycogen verses fatty acids usage in the fatty acid favor.
The result, you can theorectically run longer on the same level of glycogen stores (asumming your intensity level is not too high). This can be found by googling "glycogen depletion training" or "train low race high".
So combine that with the carb loading, you can see how marathon runners can train and eat in a way to maximize their efficiency to run long distances.
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Speaking of diet, I feel the need to discuss the low carb (high fat) diets and the argument which is better for aerobic athletes (such as long distance runners).
So the argument is that 1 gram of fat supplies 7 calories where 1 gram of glucose supplies only 4 calories. So if somehow you could train your body to use more fat than carbs, then you should have more energy. Right?
Well, in order to use fatty acids to make ATP, you need oxygen. So in order to go longer, you need to keep intensity just low enough not to exhaust oxygen in your mitochondria. Exhaust your oxygen then you will start using more carbs regardless.
So those that make the claim that they are better athletes on a high fat low carb diet cannot increase their glycogen stores above normal (like carb loaders do). So they really have to be careful not to go too hard as far as intensity or speed goes. Carb loaders have a little more forgiveness and can go out faster.
By the way, there are studies that show that glycogen stores can be refilled to normal or close to normal levels even on low carb diets due to glycogenolysis.
Edit: 1 gram of fat supplies 9 calories, not 7. ooops.
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Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
Addendum: The reference used by the U Mich monograph is not available on the internet, but these studies are probably relevant:
30. Coggan AR, Raguso CA, Williams BD, et al. Glucose kinetics during high-intensity exercise in endurance-trained and un- trained humans. J Appl Physiol 1995; 78: 1203-7
31. Coggan AR, Kohrt WM, Spina RJ, et al. Endurance training decreases plasma glucose turnover and oxidation during moderate-intensity exercise in men. J Appl Physiol 1990; 68: 990-6
32. CogganAR. Plasma glucose metabolism during exercise:effect of endurance training in humans. Med Sci Sports Exerc 1997; 29: 620-7
33. Karlsson J, Nordesjo LO, Saltin B. Muscle glycogen utilization during exercise after physical training. Acta Physiol Scand 1974; 90: 210-7
I'll try to track a couple down through the internet when I have time, or request them through a service.
The take-home point is that context matters greatly. It is a mistake to presume that the exercise physiology seen in a trained person is going to match an MFP overweight newbie trying to lose weight.0 -
[*] Non-aerobic glycolysis last 45-150 seconds. Type II, or fast-twitch muscles, are the locus for glycolysis using stored muscle glycogen.
[*] The aerobic system, known as the Kerbs Cycle, provides most of the energy for effort of 3 minutes or longer. Type I, slow-twitching muscle, in conjunction with Type IIa, provides the mechanical work. For fuel, this system relies on fat at lower intensities progressing to carbohydrate as intensity increases.
[*] The phosphagen system is used during maximal effort which only have enough supply of energy for 10 seconds. Re-phosphorylation of ADP from phosphocreatine stores provides enough for about 25 seconds total. (Structured training utilizing this pathway is HIIT not to be confused by the garbage floating around recently).
[/list]
Just so we don't confuse @rainbowbow, when we say that we use the phosphagen system and then non-aerobic glycolysis for an additional 45-90 seconds, what he is describing is what happends when you go from a complete resting state into aerobic exercise and the various stages that occur to prepare your body to meet the abrupt increased energy demands.
So your body is not geared to provide the ATP necessary to use glycoysis and Krebs Cycle and ETC right away. Too many steps have to occur to supply this energy. So there are intermediate steps that the body can use to supply you energy from when you are standing on the starting line waiting for the gun to go off and then *BOOM* you start running pretty hard.
When you are at complete rest, your body is in a somewhat homeostatious state. As soon as you start running, your muscle cells rely immediately on extra ATP that is stored. Enough to supply you with enough ATP for about 3 seconds of contraction. Just enough time to allow the creatine phosphogen system to start supplying ATP (which acts very quickly). But the phophogen system only has enough resources in the muscle cell to supply about 10 seconds worth of ATP. While this is going on, glycolysis is kick started so by the time the phosphogen system runs out of resources, glycoylysis can begin supplying enough ATP. All of the systems described do not require oxygen to make ATP. So they are anaerobic (or non-aerobic) in nature. While this is going on, the body begins to quicken the heart rate (to pump more blood) so that more oxygen can be delivered to the muscle cells. Within 90 seconds from the moment you started running, there is now an increased amount of oxygen being delivered to your muscle cells so that Krebs Cycle and ETC can do their thing. The ratio to burn glucose verses fatty acids are increased until things get settled and you then begin to burn more fatty acids than glucose (assuming your intensity level allows for this).
Got it, thanks for this! I'm taking notes now.
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ericGold15 wrote: »
Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
"Thus, MedFitness recommends that high intensity training is completed prior to aerobic exercise for individuals who are trying to maximize fat burning. This ensures that the energy needed for glycolysis is used in weightlifting. Then after 30 minutes of weightlifting, the glycogen and blood glucose have been used up and the body uses primarily fatty acids for its fuel. Switching to moderate intensity exercise lets the body consume FFA for metabolic energy and also gives the body time to remove the lactic acid so that aerobic exercise can be performed. Thus lifting weights first for 30 minutes and then doing aerobic exercises is the best way to maximize energy used in high intensity training while selectively burning fat efficiently"
correct me if i'm wrong, but isn't this above constantly being recommended throughout the forums? Isn't this common advice given for those lifting weights and doing cardio?0 -
rainbowbow wrote: »ericGold15 wrote: »
Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
"Thus, MedFitness recommends that high intensity training is completed prior to aerobic exercise for individuals who are trying to maximize fat burning. This ensures that the energy needed for glycolysis is used in weightlifting. Then after 30 minutes of weightlifting, the glycogen and blood glucose have been used up and the body uses primarily fatty acids for its fuel. Switching to moderate intensity exercise lets the body consume FFA for metabolic energy and also gives the body time to remove the lactic acid so that aerobic exercise can be performed. Thus lifting weights first for 30 minutes and then doing aerobic exercises is the best way to maximize energy used in high intensity training while selectively burning fat efficiently"
correct me if i'm wrong, but isn't this above constantly being recommended throughout the forums? Isn't this common advice given for those lifting weights and doing cardio?
Depends on what you are more concerned about. If you are a more serious weight lifter or someone more concerned about losing weight, then what you described makes sense.
As a runner who uses strength training to help me with running, I am more concerned about preserving my energy for a more intense run. So the way I do things may be a little different.0 -
rainbowbow wrote: »ericGold15 wrote: »
Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
"Thus, MedFitness recommends that high intensity training is completed prior to aerobic exercise for individuals who are trying to maximize fat burning. This ensures that the energy needed for glycolysis is used in weightlifting. Then after 30 minutes of weightlifting, the glycogen and blood glucose have been used up and the body uses primarily fatty acids for its fuel. Switching to moderate intensity exercise lets the body consume FFA for metabolic energy and also gives the body time to remove the lactic acid so that aerobic exercise can be performed. Thus lifting weights first for 30 minutes and then doing aerobic exercises is the best way to maximize energy used in high intensity training while selectively burning fat efficiently"
correct me if i'm wrong, but isn't this above constantly being recommended throughout the forums? Isn't this common advice given for those lifting weights and doing cardio?
Depends on what you are more concerned about. If you are a more serious weight lifter or someone more concerned about losing weight, then what you described makes sense.
As a runner who uses strength training to help me with running, I am more concerned about preserving my energy for a more intense run. So the way I do things may be a little different.
Yes, that's true! I think I see this scenerio less often on myfitnesspal, but that makes perfect sense!0 -
rainbowbow wrote: »ericGold15 wrote: »
Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
"Thus, MedFitness recommends that high intensity training is completed prior to aerobic exercise for individuals who are trying to maximize fat burning. This ensures that the energy needed for glycolysis is used in weightlifting. Then after 30 minutes of weightlifting, the glycogen and blood glucose have been used up and the body uses primarily fatty acids for its fuel. Switching to moderate intensity exercise lets the body consume FFA for metabolic energy and also gives the body time to remove the lactic acid so that aerobic exercise can be performed. Thus lifting weights first for 30 minutes and then doing aerobic exercises is the best way to maximize energy used in high intensity training while selectively burning fat efficiently"
correct me if i'm wrong, but isn't this above constantly being recommended throughout the forums? Isn't this common advice given for those lifting weights and doing cardio?
So now 30 minutes of weightlifting apparently uses as much glycogen as 30 minutes of sustained cardio, which is apparently all of it, but not really.
This thing eric posted gets more and more confusing.0 -
rainbowbow wrote: »ericGold15 wrote: »
Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
"Thus, MedFitness recommends that high intensity training is completed prior to aerobic exercise for individuals who are trying to maximize fat burning. This ensures that the energy needed for glycolysis is used in weightlifting. Then after 30 minutes of weightlifting, the glycogen and blood glucose have been used up and the body uses primarily fatty acids for its fuel. Switching to moderate intensity exercise lets the body consume FFA for metabolic energy and also gives the body time to remove the lactic acid so that aerobic exercise can be performed. Thus lifting weights first for 30 minutes and then doing aerobic exercises is the best way to maximize energy used in high intensity training while selectively burning fat efficiently"
correct me if i'm wrong, but isn't this above constantly being recommended throughout the forums? Isn't this common advice given for those lifting weights and doing cardio?stevencloser wrote: »So now 30 minutes of weightlifting apparently uses as much glycogen as 30 minutes of sustained cardio, which is apparently all of it, but not really.
This thing eric posted gets more and more confusing.
This is my interpretation. So if you are concerned more about performance then yes. This takes advantage of more fat for energy.
Weight lifting is more anaerobic in nature (high intensity with rest in between) versus low/medium intensity sustained cardio which is more aerobic in nature.
So within that time period of when you are at the gym (the weight lifting and cardio) you would theorectically maximize the use of fat (while making quite a few assumptions). First assumption is that your cardio is at an intensity where oxygen use is not fully exhausted to make you go back into a higher ratio of carb burning. Second, that your intensity during the weight lifting session is hard.
But in the grand scheme of things, as the OP originally stated. So what? At the end of the day you will eat those calories back and glycogen stores will get refreshed. If you ate more calories than needed during the day, then the fat stores get replaced (and may even grow). So no matter what was used more, fat or sugar, it comes back to what you eat in the day. You have to think the entire 24 hour period, not just the 2 or 3 hours you spent in the gym.
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ericGold15 wrote: »
Don't giggle too much over what you do not understand.ericGold15 wrote: »
Or not. From 'MedFitness, associated with the U of Michigan:.Glycogen isn't used first - the vast majority of exercise is fuelled from a blend of fat and glycogen (carbohydrate) in differing proportions. During lower intensity exercise fat is the predominant fuel, higher intensity carbohydrate is the predominant source. If I remember correctly the 50/50 point is roughly 70% of max HR but sure someone can correct me.Exercising for longer than 30 minutes shifts the primary macromolecules that are metabolized from glucose to fatty acids. Shifting from glucose and glycogen supplies allows the body to efficiently mobilize and utilize free fatty acids (FFAs) derived from lipids in adipose tissue, which resides mainly under the skin.
... ...
After the first 30 minutes of exercise, the body runs out of its glycogen storage and then turns mainly to what is left of the glucose in the blood and then finally to fat and amino acids derived from muscle protein. Supporting evidence of fatty acid release comes from physiologic research where human gluteal fat cells isolated after 30 minutes of biking showed that cathecholamine induced lipolysis had increased between 35-50% 4. If exercise does not last until 30 minutes then fat burning is never achieved because all of the glycogen is not used u p. So while one may be able to prevent adding fat to the body, one is not metabolizing fat from the adipose tissues during the exercise. In short, exercises aerobically for less than 30 minutes, one is just maintaining the adipose tissue status quo and decreasing muscle mass.
Thanks for the giggles - that article is hilarious!
Running out of glycogen storage after 30 minutes - really?
During a 20 minute VO2 max test I went from RER of 0.82 during the gentle start (0.7 is totally fat fuelled) progressively through to RER of 1.0 (totally carb fuelled) after about 15 minutes building to very high intensity and eventually anaerobic at maximal effort / failure.
The monograph I quoted is about the same level of the longer posts here that attempt to summarize some basic biochemistry and exercise physiology, except that it was vetted by a PhD advisor. If you dispute the message then critique the attached bilbliography that is used to support the summary.
Yes, I agree that 500 grams of glycogen is not consumed in 15 minutes of moderate exercise, and "use up the glycogen" should not be read to mean that. The message is that in moderate exercise there will be a preferential use of glycogen in the beginning, I presume even without carb loading but obviously not in a prolonged fast scenario.
So far as I know these kinetic studies are based on respiratory quotients; perhaps other methods have come along that I have not read. Is RER an RQ ? If you are quoting RQs in your personal anecdote then I agree with your interp that your initial exercise was not CHO fueled. <<shrug>> I can think of possible explanations why but it would just be conjecture without more data.
I was thinking about RQ as a method the other day. What is the RQ of muscle breakdown ? Do you know ? I'll guess close to carb since they have similar energy contents per gram but in any case it is not obvious to me how kinetic RQ studies separate out protein from the mix of fat and carb use.
Addendum: The reference used by the U Mich monograph is not available on the internet, but these studies are probably relevant:
30. Coggan AR, Raguso CA, Williams BD, et al. Glucose kinetics during high-intensity exercise in endurance-trained and un- trained humans. J Appl Physiol 1995; 78: 1203-7
31. Coggan AR, Kohrt WM, Spina RJ, et al. Endurance training decreases plasma glucose turnover and oxidation during moderate-intensity exercise in men. J Appl Physiol 1990; 68: 990-6
32. CogganAR. Plasma glucose metabolism during exercise:effect of endurance training in humans. Med Sci Sports Exerc 1997; 29: 620-7
33. Karlsson J, Nordesjo LO, Saltin B. Muscle glycogen utilization during exercise after physical training. Acta Physiol Scand 1974; 90: 210-7
I'll try to track a couple down through the internet when I have time, or request them through a service.
The take-home point is that context matters greatly. It is a mistake to presume that the exercise physiology seen in a trained person is going to match an MFP overweight newbie trying to lose weight.
But I do understand exercise physiology - I have a particular interest in the practical application of it as a long distance cyclist. Knowing how to correctly fuel rides makes a huge difference.
My personal anecdote as you call it is exactly what you would expect to see, it's a standard testing protocol. Nothing unusual in the results at all.
A question - you must have found many articles far better written and explaining fuel usage accurately so wonder why you fixated on this one and choose to defend it? Is there another agenda going on?
Do you follow a low carb or keto regime perhaps?0 -
So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?0
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Sorry -- I don't know the common call on MFP. The approach seems rational to me -- if you manage it.rainbowbow wrote: »correct me if i'm wrong, but isn't this above constantly being recommended throughout the forums? Isn't this common advice given for those lifting weights and doing cardio?
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I follow neither. Truthfully I don't follow any fad, and for my primary goal of fitness I think the nitpicking over macros rather than eating a nutritious an varied diet is silly. I just eat enough protein, know that I get RDA of the important minerals and vitamins, and go along my happy vegetarian way. My diet ends up being low fat because of the foods I like to eat. I eat snap peas the way some people eat popcorn.Do you follow a low carb or keto regime perhaps?
So a big NO to a personal agenda. I have read a fair amount of exercise physiology though not much recently, and I still remember some biochemistry. And I'm always happy to read an original study and discuss it rather than get annoyed at bro science inside an echo chamber.
I posted the U Mich monograph because I thought it was readable for others and because it had a bibliography. As Anvil found out, I am as likely to post a study that contradicts me as not because I am not trying to be "right" or pursue an agenda, but to sometimes try to give an overview, sometimes to show how uncertain a topic is, sometimes to emphasize the context, and sometimes because it discusses an aspect of physiology I wanted to highlight.
You will get a headache trying to pigeon-hole me. I recommend instead that you just bring interesting studies.
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ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
Move! and for a while. Doesn't matter how, you use enough energy to raise your heart rate for 30 minutes, your blood glucose will exhaust (it will get replaced but any excess directly from diet will deplete).0 -
Ok thanks.ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
Move! and for a while. Doesn't matter how, you use enough energy to raise your heart rate for 30 minutes, your blood glucose will exhaust (it will get replaced but any excess directly from diet will deplete).
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ericGold15 wrote: »
I follow neither. Truthfully I don't follow any fad, and for my primary goal of fitness I think the nitpicking over macros rather than eating a nutritious an varied diet is silly. I just eat enough protein, know that I get RDA of the important minerals and vitamins, and go along my happy vegetarian way. My diet ends up being low fat because of the foods I like to eat. I eat snap peas the way some people eat popcorn.Do you follow a low carb or keto regime perhaps?
So a big NO to a personal agenda. I have read a fair amount of exercise physiology though not much recently, and I still remember some biochemistry. And I'm always happy to read an original study and discuss it rather than get annoyed at bro science inside an echo chamber.
I posted the U Mich monograph because I thought it was readable for others and because it had a bibliography. As Anvil found out, I am as likely to post a study that contradicts me as not because I am not trying to be "right" or pursue an agenda, but to sometimes try to give an overview, sometimes to show how uncertain a topic is, sometimes to emphasize the context, and sometimes because it discusses an aspect of physiology I wanted to highlight.
You will get a headache trying to pigeon-hole me. I recommend instead that you just bring interesting studies.
Thank you - just found it curious that you selected an article that is either spectacularly badly written or just plain at variance with known science. Not having a go at you but when the author writes "After the first 30 minutes of exercise, the body runs out of its glycogen storage" then both the author and the article simply has no credibility at all.
Off to the gym now, my exercise will be fuelled by pork and apricot casserole and duchess potatoes. I don't expect to bonk after 30 minutes!0 -
^^ I agree that a literal reading is wrong. I read it as meaning that for the groups studied after 30 minutes the signaling to increase fat burn kicks in. Since glycogen is compartmentalized into different environments, it's breakdown affected by different signals and at different rates, I gave the author the benefit of the doubt that a specific compartment was being mentioned. I'll guess that she was referring to the exercising muscles but I'll have to dig a bit to be sure.0
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ericGold15 wrote: »
I agree with the first part of your post, but this second part is more in the 'mostly true' category.rankinsect wrote: »A related myth is the 'fat burning zone' on cardio equipment. Basically, that is the target heart rate that produces the greatest ratio of calories from fat vs. calories from glycogen or other sources. However, again, this is TBI - the actual way to burn the most fat is to burn the most total calories, regardless of where the calories come from, because in the long term the source of the energy is irrelevant.
I think a better analogy is savings in different types of accounts: checking, savings, IRA, stocks and finally your home.
Depending how full your glycogen account is when you start exercise, it will be used first but not to empty. I am not positive, but I think the tendency towards preferential glycogen use depends on where it is stored. Muscle glycogen seems to be readily and preferentially used. Liver glycogen use kicks in somewhere along the line but not to exhaustion before the body starts providing substantial energy from fat burn.
The 'fat burning zone' kicks in after the easily accessible glycogen is used. The reason to not exceed the zone has to do with a body's maximum fat burn rate. If the demand is greater than the fat burn the body will deplete glycogen further and start to recruit protein breakdown.
Your general point however is spot on: exercise more, lose more fat for a constant calorie intake.
While other factors can shift RQ (ratio of carb/fat oxidation) a little, carb/fat burning is primarily dictated by intensity of exercise, not by carbohydrate storage. And you are always burning a combination of fats and carbs--there is no "shift" in metabolism from one substrate to the other.
If you are performing at a high intensity and run out of glycogen (aka "hit the wall") the body doesn't shift over to fats and you continue on your merry way. There is an immediate and significant degradation of performance since fat metabolism can only support an intensity of about 50% of VO2 max. Training the body to improve "fat burning" has nothing to do with body fat loss and everything to do with performance in an endurance event.
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ForecasterJason wrote: »
Ok thanks.ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
Move! and for a while. Doesn't matter how, you use enough energy to raise your heart rate for 30 minutes, your blood glucose will exhaust (it will get replaced but any excess directly from diet will deplete).
Well, except it might not, because blood glucose can rise in IR due to immediate exercise, as you've seen. It's a conundrum, imho, because I don't like seeing my levels get higher after exercise, either. But it's totally normal, and exercise helps glucose levels overall.
I got lovely drops in BG after walking, so that's one option. But then I added in sprints, which really do challenge my heart more, etc. That's when my BG started going up after exercise instead of lowering. It was vigorous enough to count as 'stress' to the body. That's why BG goes up after some exercise.
OTOH, sprinting like I do has been proven to really help IR (overall). So the only 'problem' is the high BG afterwards, which is normal. I say screw it. I try not to eat carbs for those 2 hours, but otherwise I know that the sprinting is a good thing to add, higher BG for an hour or two be damned.
It would be interesting if anyone knows how we should handle eating around exercise. It seems to be trial and error, but surely someone knows the biochemistry of it when it includes insulin resistance, liver glucose dumps, etc. I've never seen it explained. What I've read feels pretty vague, like the 'stress' thing. It's true, probably, but vague.0 -
Very interesting!
This plays back in to lactate threshold test training.
The hardest pace I can maintain for an hour.
The fat burning zone is part of my training twice a month for long ride/run events. We do 40 miles ride/10K runs now every weekend, but in the spring it gets up to 80 miles and 15K twice a month. All at Z2 HRM max using a heart rate monitor as the driver of the training.
There is something to be said for the zone 2 heart rate training, but I think when you plan 6 hours of exertion it becomes pretty critical to manage heart rate and exertion levels.
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I can tell I am old because I cannot fathom all of this. I have degenerated to the point where I run and workout so I can drink like a fish and eat whatever I want.0
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cafeaulait7 wrote: »ForecasterJason wrote: »
Ok thanks.ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
Move! and for a while. Doesn't matter how, you use enough energy to raise your heart rate for 30 minutes, your blood glucose will exhaust (it will get replaced but any excess directly from diet will deplete).
Well, except it might not, because blood glucose can rise in IR due to immediate exercise, as you've seen. It's a conundrum, imho, because I don't like seeing my levels get higher after exercise, either. But it's totally normal, and exercise helps glucose levels overall.
I got lovely drops in BG after walking, so that's one option. But then I added in sprints, which really do challenge my heart more, etc. That's when my BG started going up after exercise instead of lowering. It was vigorous enough to count as 'stress' to the body. That's why BG goes up after some exercise.
OTOH, sprinting like I do has been proven to really help IR (overall). So the only 'problem' is the high BG afterwards, which is normal. I say screw it. I try not to eat carbs for those 2 hours, but otherwise I know that the sprinting is a good thing to add, higher BG for an hour or two be damned.
It would be interesting if anyone knows how we should handle eating around exercise. It seems to be trial and error, but surely someone knows the biochemistry of it when it includes insulin resistance, liver glucose dumps, etc. I've never seen it explained. What I've read feels pretty vague, like the 'stress' thing. It's true, probably, but vague.
OK! I will make an attempt. Good constructive criticism from the peanut gallary will help me learn.
So we have a conumdrum.
Excess floating BG (blood glucose) floating around. I will assume this is because we ate a lot of carbs (tho not necessarily but makes a good starting point). So we decide to run this off.
In practice, running requires energy (energy from the BG). We use that BG to pump into glycolysis and we make a bunch of ATP (assuming we have lots of oxygen as well so Krebs and ETC can also do their thing) and wa-lah we reduce BG. But wait! We ran so hard that cortisol got dumped into the blood. What is cortisol? It's a harmone that the pancrease releases when the body takes on a lot of stress. It's the anti-insulin harmone. While insulin acts like a traffic cop (or an usher in the theater) directing BG into the cell either to use for Glycolysis, or to produce more glycogen, or to convert BG into triglycerol and store it in andipose as fat. Cortisol does the opposite. It stops insulin from what it is doing (keeping BG out of the cell and make it stay in the blood) and it encourages the liver to release more glucose (from the glycogen it is storing). Cortisol does this because we assume we are going to need a lot of energy to overcome stress.
If you were walking along in the jungle minding your own business and all of a sudden a cheetah just comes darting at you. That causes stress. The body reacts to stress by releasing stress harmones like adrenaline and cortisol. because... well we are going to need a lot of energy to out run the cheetah. (just work with me on this)
Well, that is just one kind of stress. Sitting at your desk doing nothing (physically speaking) worrying about that deadline is another form of stress. Your brain will need a lot of energy to help you think of how you are going to work on your project so you can meet your deadline. Your brain doesn't need as much energy as it would say to outrun that cheetah, but... your body really doesn't know the difference. it just knows stress. And stress will require more energy. So lets release the crackin of harmones that will get us that energy.
So you do sprints. God I hate sprints. Just thinking about sprints causes... stress! Wait! Stress causes insulin levels to decrease, which is the thing that helps BG go into the cell and increases cortisol which actually releases more BG into the blood. What is going on? Ahhhhhhhhh!
Well, we need a super hero. Glut-4 to the rescue. Well, the way insulin works is that it kind of knocks on the door of a muscle cell. The insulin receptor (IR) answers the door and says ahhhh! Insulin is here, let me bring Glut-4 to the other door so glucose can enter in. Well if Insulin levels decrease, no one is knocking on the door. So how can BG enter the cell? Well, there is something called exercise induced Glut-4. When contraction happends and ATP levels decrease in the muscle cell, another Glut-4 is sent from within the cell to go to the door to let glucose in.
I am still trying to figure how this works for fatty acids, so if anyone knows, can you give me a hint?
But my long story (well my contribution) is insulin and cortisol and how 2 different kinds of Glut-4 inside your muscle cell works. So if you want to get rid of excess BG, you need exercise, but for God sakes don't stress about it. or else you will have a conumdrum on your hands.
This may explain why walking gets rid of your excess BG but the sprints don't or may actually add more BG.
I don't know. We need more biology nerds in here to help out.
Edited to correct a whole bunch of stuff because I type faster than I can think coherently.0 -
cafeaulait7 wrote: »OTOH, sprinting like I do has been proven to really help IR (overall). So the only 'problem' is the high BG afterwards, which is normal. I say screw it. I try not to eat carbs for those 2 hours, but otherwise I know that the sprinting is a good thing to add, higher BG for an hour or two be damned.
So the problem with not eating carbs for 2 hours after exercise is that you are missing out on the recovery meal. High glucose uptake to replace the used up glycogen within the 30 minute window right after you get done with exercise. It probably has to do with that whole exercise induced Glute-4 thingy and the chemical/harmonal cocktail that results from that intense exercise you just performed.
In a healthy person, eating hi-glycemic carbs immediately after exercise will get shuttled into your muscle cell to restore that muscle glycogen that got used up and add some quick absorbing protein into the mix, those amino acids will jam packed in as wel to really boost your recovery. cause exercise causes tiny miscroscopic tears in your muscles and we need energy (glycogen) and amino acids to repair that damage. And the faster we can jam that glucose and AA into the cell, the faster we can repeair the damage. And since we have a super period of 30 minutes from the moment we get done exercising till we get fully rested, we have a small window to really jam them in.
If we dare to ignore this window, then later on this damage to our muscle cell will cause hunger. Hunger causes us to eat (and sometimes overeat) because the more you exercise the more intense hunger results. Experiment (walk in the park for a little bit and see how hungry you get in 2 hours. Now run sprints (like 5 miles worth) up some major hills and see how hungry you get in 2 hours.
So research has been done that if you eat some quick carbs and quick absorbing protein immediately after exercise (like within that 30 minute window) that hunger later on is actually controlled. Cause that muscle cell that is damaged got some really good satisfaction and won't ring the hunger alarm quite as hard. Experiment: run those same sprints and immeditely eat something within 30 minutes and see how hungry you get in 2 hours.
So... you have some kind of insulin resistance problem where dangling BG is a problem. Kind of breaching my level of understanding. But I can see how this can be a problem and causes some major conumdrum issues.0 -
MorningGhost14 wrote: »I can tell I am old because I cannot fathom all of this. I have degenerated to the point where I run and workout so I can drink like a fish and eat whatever I want.
I like this thought. Too bad I am an engineer (software and systems engineer) and I just love solving problems that really don't exist way too much.
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Run a few full out sprints. Basically a short bout of high intensity exercise.ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
A.C.E. Certified Personal and Group Fitness Trainer
IDEA Fitness member
Kickboxing Certified Instructor
Been in fitness for 30 years and have studied kinesiology and nutrition
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Just a couple of quick points:
If one is "hitting the wall" after 90 minutes of exercise, the exercise is either too intense to do, one is on a very low carb diet or the performer isn't replenishing carbs to finish (endurance athlete usually).
Fat is the primary source of fuel at rest. If your sleeping and rest sucks, chances are you're disrupting efficient fat burning. You will burn the majority of your body fat from rest and not exercising because we are more at rest during the day than exercising.
Carbs aren't bad. While many do low carb and rely on ketosis to fuel workouts, workout are much more efficient for anyone if they have ample glycogen supply for carb ingestion to endure a moderate intensity 90 minute workout. That's not to say that some low carbing can't do it. Just saying that same person would likely be more efficient in their workouts with carb intake previous to intense exercise.
A.C.E. Certified Personal and Group Fitness Trainer
IDEA Fitness member
Kickboxing Certified Instructor
Been in fitness for 30 years and have studied kinesiology and nutrition
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This is well written. I think the part I bolded is what applies to my case, which would explain why I have always been able to maintain low body fat but yet my BG not being controlled as properly as it should be. I suspect that my cortisol level probably stays elevated during the school year, keeping more than appropriate amounts of glucose in the bloodstream.cafeaulait7 wrote: »ForecasterJason wrote: »
Ok thanks.ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
Move! and for a while. Doesn't matter how, you use enough energy to raise your heart rate for 30 minutes, your blood glucose will exhaust (it will get replaced but any excess directly from diet will deplete).
Well, except it might not, because blood glucose can rise in IR due to immediate exercise, as you've seen. It's a conundrum, imho, because I don't like seeing my levels get higher after exercise, either. But it's totally normal, and exercise helps glucose levels overall.
I got lovely drops in BG after walking, so that's one option. But then I added in sprints, which really do challenge my heart more, etc. That's when my BG started going up after exercise instead of lowering. It was vigorous enough to count as 'stress' to the body. That's why BG goes up after some exercise.
OTOH, sprinting like I do has been proven to really help IR (overall). So the only 'problem' is the high BG afterwards, which is normal. I say screw it. I try not to eat carbs for those 2 hours, but otherwise I know that the sprinting is a good thing to add, higher BG for an hour or two be damned.
It would be interesting if anyone knows how we should handle eating around exercise. It seems to be trial and error, but surely someone knows the biochemistry of it when it includes insulin resistance, liver glucose dumps, etc. I've never seen it explained. What I've read feels pretty vague, like the 'stress' thing. It's true, probably, but vague.
OK! I will make an attempt. Good constructive criticism from the peanut gallary will help me learn.
So we have a conumdrum.
Excess floating BG (blood glucose) floating around. I will assume this is because we ate a lot of carbs (tho not necessarily but makes a good starting point). So we decide to run this off.
In practice, running requires energy (energy from the BG). We use that BG to pump into glycolysis and we make a bunch of ATP (assuming we have lots of oxygen as well so Krebs and ETC can also do their thing) and wa-lah we reduce BG. But wait! We ran so hard that cortisol got dumped into the blood. What is cortisol? It's a harmone that the pancrease releases when the body takes on a lot of stress. It's the anti-insulin harmone. While insulin acts like a traffic cop (or an usher in the theater) directing BG into the cell either to use for Glycolysis, or to produce more glycogen, or to convert BG into triglycerol and store it in andipose as fat. Cortisol does the opposite. It stops insulin from what it is doing (keeping BG out of the cell and make it stay in the blood) and it encourages the liver to release more glucose (from the glycogen it is storing). Cortisol does this because we assume we are going to need a lot of energy to overcome stress.
If you were walking along in the jungle minding your own business and all of a sudden a cheetah just comes darting at you. That causes stress. The body reacts to stress by releasing stress harmones like adrenaline and cortisol. because... well we are going to need a lot of energy to out run the cheetah. (just work with me on this)
Well, that is just one kind of stress. Sitting at your desk doing nothing (physically speaking) worrying about that deadline is another form of stress. Your brain will need a lot of energy to help you think of how you are going to work on your project so you can meet your deadline. Your brain doesn't need as much energy as it would say to outrun that cheetah, but... your body really doesn't know the difference. it just knows stress. And stress will require more energy. So lets release the crackin of harmones that will get us that energy.
So you do sprints. God I hate sprints. Just thinking about sprints causes... stress! Wait! Stress causes insulin levels to decrease, which is the thing that helps BG go into the cell and increases cortisol which actually releases more BG into the blood. What is going on? Ahhhhhhhhh!
Well, we need a super hero. Glut-4 to the rescue. Well, the way insulin works is that it kind of knocks on the door of a muscle cell. The insulin receptor (IR) answers the door and says ahhhh! Insulin is here, let me bring Glut-4 to the other door so glucose can enter in. Well if Insulin levels decrease, no one is knocking on the door. So how can BG enter the cell? Well, there is something called exercise induced Glut-4. When contraction happends and ATP levels decrease in the muscle cell, another Glut-4 is sent from within the cell to go to the door to let glucose in.
I am still trying to figure how this works for fatty acids, so if anyone knows, can you give me a hint?
But my long story (well my contribution) is insulin and cortisol and how 2 different kinds of Glut-4 inside your muscle cell works. So if you want to get rid of excess BG, you need exercise, but for God sakes don't stress about it. or else you will have a conumdrum on your hands.
This may explain why walking gets rid of your excess BG but the sprints don't or may actually add more BG.
I don't know. We need more biology nerds in here to help out.
Edited to correct a whole bunch of stuff because I type faster than I can think coherently.
Thanks
Run a few full out sprints. Basically a short bout of high intensity exercise.ForecasterJason wrote: »So, to summarize my earlier question: What would be the best way from an exercise standpoint to remove excess circulating glucose (though not necessarily stored body fat)?
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