Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
20 Oct

Dear Mark: Glycogen

394740182 bb2fea1039Dear Mark,

I’m trying to understand how glucose that’s created by proteins and fats is used and stored. Is that ~200g of glycogen stored in the muscles to be used for exercise, or is it stored in the liver and used to fuel the brain and “day-to-day” functions? Also, if muscle glycogen is depleted, will ingested carbohydrates be used first to replenish muscle glycogen and then to fuel other daily functions, or are they used the other way around? I’d like to be able to use ketones to fuel my daily activity, but still have enough muscle glycogen stores to fuel intense exercise.

I always appreciate comments and questions that spur more explanation and discussion about the body’s functioning. Let’s take this one apart and have a look. Fat is always the best fuel to use at low levels of effort. We evolved to be very efficient fat-burners and even those of us at single-digit body fat levels have plenty to spare. Glycogen, as you remember, is stored glucose and is the body’s first-line energy stockpile of fuel for harder physical efforts and keeping specific systems (brain, red blood cells, kidney cells) running efficiently all day. It’s stored primarily in the liver and muscles; however, (of the two) only the glycogen stores of the liver can be used by the rest of the body. The muscles can’t share their stores. Selfish, you might say, but that’s how it works. As you suspect, the glycogen stored in the muscles (provided you aren’t taking in other glucose) is used along with fats to fuel physical activity throughout the day like your work out, your daily walk to the train, walk to the fridge, etc. The glycogen in the liver, while it can contribute circulating glucose to working muscles, generally serves up energy (reconverted glucose) to other parts of the body – the brain for example – as it sees fit.

As to the question of whether ingested carbs will go first to the muscles or to other functioning, it depends on lifestyle and how much you rely on carbs. If you are training hard every day and depending on a high-carb diet, the muscles will probably do a better job of storing those first incoming carbs from a meal eaten right after the workout. On the other hand, in the case of a low-carb strategy, the 200 grams a day you refer to are made in the liver via gluconeogenesis and mostly stored there to provide energy for vital functions. Yes, some will go to muscles recovering from a Primal-style brief-but-intense effort, but the rest stays in the liver and provides glycogen/glucose for the brain and red blood cells, etc.

Ultimately, though, this line caught my eye the most: I’d like to be able to use ketones to fuel my daily activity, but still have enough muscle glycogen stores to fuel intense exercise. I’d suggest looking at this kind of goal from a different angle. You really can’t have it both ways. Because you can’t override your body organs’ pecking order, it becomes a choice of either doing a ketogenic diet, which puts all your systems on an alternative fuel burning plan, or doing a moderately low carb diet that provides just enough glucose for your brain’s needs and for intense exercise bouts of an hour or less (centerpieces of the Primal Blueprint). If you’re looking to lose weight (fat), the ketogenic diet will be the most dramatically and swiftly successful. If you’re happy with the weight or are OK with a more gradual move toward your “ideal” body composition, the moderate-low path may be the way to go.

Finally, if it’s a question of fueling longer aerobic workouts (long distance running, for example), I’d suggest what I’ve said in the past. Endurance athletes, while they don’t need to indulge in the worst of the traditional carb loading, will need to make compromises to the Primal style. If they are “classically trained” in doing long workouts at 75-90% VO2 max, their bodies will simply require more glucose (and, hence, muscle glycogen) to accomplish the feats asked of them. In that case, ketones can’t play much of a role. On the other hand, it is possible – over a long period of time – to redirect gene expression to favor fat and ketone metabolism even at higher workloads. But this requires that the training be done at much lower heart rates for longer periods of time. That becomes the only way to recommend endurance athletes adapt their training and diet regimens to maximize fat burning efficiency. Check out Primal Compromises for Athletes for more on that discussion.

As always, thanks for your questions and keep ‘em coming!

Bob.Fornal Flickr Photo (CC)

Further Reading:

The Definitive Guide to the Primal Eating Plan

What Happens to Your Body When… You CARB BINGE?

The Context of Calories – 200 Calories is 200 Calories. Right?

Dear Mark: Did Our Bodies Evolve to Run on Ketones?

The Entire Definitive Guide Series

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Good read. As I like to tell people, eat enough carbs just to keep you awake and muscles fueled for explosive work that day and then use fat to burn all day long. Best time to reload is of course after muscle glycogen depletion exercise (more resistance training, not endurance) when they are more primed for intake (which of course is not every day too). Meat+Fat+Veggies most the time…..Meat+Carbs postworkout recovery as needed. Of course if fat loss is the goal one must be careful of carb levels pwo, as too much will just create a spillover effect and store in the fat cells instead.

    Mike OD - IF Life wrote on October 20th, 2008
  2. I always thought the ketogenic diet worked on a gradual sliding scale rather than an either/or. So then the question becomes, at what point does the body make the switch from burning carbs to ketones? I’m assuming it’s different for every body, but would the number typically be under 100 carbs/day or under 20 carbs/day?

    Bud wrote on October 20th, 2008
  3. Great information. Thanks. I also echo Bud’s question – although, as he does, I suspect it’s different for everyone!

    Alex wrote on October 20th, 2008
  4. The classic ketogenic diet, from my understanding, is comprised of 88% fat, 10% proteins and 2% carbohydrates. So the exact number does depend on how many calories one consumes.

    Holly wrote on October 20th, 2008
  5. Interesting topic. What would you recommend for someone who has big weight to lose? This person is 47-49 YO, male, and has at least 150 lbs. to lose. I would like to help him reach his goal. Any info pertaining to this subject would be greatly appreciated. My key questions are how many cals per day, protien, fat, and card brake down, and how long can one stay on the ketogenic diet
    Thank you.

    Tee wrote on October 20th, 2008
  6. Tee –

    Read this: http://www.marksdailyapple.com/definitive-guide-to-the-primal-eating-plan/

    It is a good starting point. Also, the Primal Health Challenge Series could stand as inspiration:

    http://www.marksdailyapple.com/30-day-primal-health-challenge-final-results/

    To lose weight quickly cut carbs over time until you get down to approximately <50 g of carbs/day. Maintain this level of carb intake while losing weight and then slowly ramp up to between 100-150 g carbs/day for the long term. Truth be told most anyone that is overweight is going to lose weight by eating the right foods and keeping carb intake to that 100-150 g/day level. Cutting them further will just make the weight come off quicker. Also, be warned that some people experience a few weeks of fatigue at the beginning of making the switch from high carb to low carb. But most will also tell you that the long term gains and balanced, sustained energy levels to come are well worth a few weeks of lethargy while your body adapts.

    Aaron wrote on October 20th, 2008
  7. Bud, you are correct that the body works on a sliding scale here. We are always making some ketones, but that is very little when we have a high carb diet. As we lower carbs, we ramp up the ketone contribution a little…but fatty acids are still providing the bulk of energy. The problem in the question above has to do with exercise. When we exercise at high intensities, we generally call upon the glucose machinery to fuel the efforts. Then we feel the need to replace the glucose with a ton of carbs. That cycle just keeps repeating and gives our genes little or no signal to “ramp up” ketone metabolism (no need to – since ketones were “designed” by evolution to spare muscle proteins during glucose starvation, and we clearly aren’t starving for glucose in that scenario).

    As an athlete, as you gradually decrease carbs and increase low-level training (very low), you can redirect the signals to call upon more beta oxidation of fats and more ketones. Eventually, you can retrain yourself to perform quite nicely on far fewer carbs and depend seriously on fats and ketones to fuel longer efforts. So you are right in that it’s not exactly an “either or” shift that happens overnight. I was trying to address the question whether you could use ketones to fuel your daily activity and save your glycogen for hard work. You can’t do that. I guess you could use fatty acids for daily activity and glycogen for work….or you could do what I have described herein and go low carb and use fatty acids for daily activity and fatty acids plus ketones for endurance. But you can’t really mix and match ketones and glucose, since the one kinda precludes the other at high intensities. make sense?

    Mark Sisson wrote on October 20th, 2008
  8. Indeed it makes sense! Very well explained, never really understood ketones until today.

    Bud wrote on October 20th, 2008
  9. Just wondering if you could consider a diet with 60-80 grams of carbs but 30 grams of fiber ketogenic since the net carbs will be a bout 30-50?

    JE Gonzalez wrote on October 20th, 2008
  10. JE, that would certainly be ketogenic provided your protein is at less than 150 grams a day (since excess protein converts to glucose).

    Mark Sisson wrote on October 20th, 2008
  11. This post made me go back and count how many carbs I am getting in a day because honestly I haven’t been calorie counting because all I usually eat is good food. I was worried after reading this because I usually have 1/2 a grapefruit and either an apple or banana every day so I thought maybe I had too much fruit. By my calculations, even with all the fruit and veggies, I am still in the 100-150g (closer to right around 100) of carbs per day range which is refreshing!

    Son of Grok wrote on October 20th, 2008
  12. Son, most people who cut all grains, simple sugars, desserts, potatoes, etc and just rely on veggies and fruit still fall below the 150 grams/a day line, eveb if they have fairly ample servings of those…so it’s a whole lot easier to be Primal than most skeptics think.

    Mark Sisson wrote on October 20th, 2008
    • Absolutely! Since going primal, I don’t count carbs or calories at all. I just try to eat primal foods. I eat as much as I want. In the 13 weeks I’ve been doing this, I’ve dropped 13 pounds. ….really without trying. The only effort is avoiding high carb foods in our world. And they are tasty. But if you’re FULL on good primal foods it’s not that hard. I can say no to a burrito with a white flour tortilla, beans and rice, because I just had a steak and broccoli dinner. :)

      Fixed Gear wrote on June 15th, 2009
  13. I have never counted calories, or grams of carbs. I have found that on a near PB diet, I simply eat what I feel I should eat (Veg, fruit, protein, fat, and/or tubers), based on how my body feels. Going by feel is one of the best things about the PB diet – your body tells you what you want!

    Ryan wrote on October 21st, 2008
  14. I was eating a banana when i pulled up your site. and then i looked at it and it was the same sticker.

    get out of my house, mark.

    Kelly Turner
    http://www.groundedfitness.com

    Grounded Fitness wrote on October 21st, 2008
  15. Kelly, didn’t mean to spook you. Guess you were meant to read that post!

    Mark Sisson wrote on October 21st, 2008
  16. When you talk about how you can’t have it both ways in relation to “ketones to fuel my daily activity…” and “muscle glycogen stores to fuel intense exercise”, is that the answer to why you can’t burn fat and build muscle at the same time?

    Thanks for the post!

    All the Best,

    Andrew R

    Andrew R wrote on October 23rd, 2008
  17. Andrew, you actually can build muscle and burn fat at the same time – just not so easily while you are focused on a ketone-based metabolism. Under normal low carb (high fat and moderate protein) circumstances you can easily build muscle working out and still burn fats. Remember, you don’t have to be in ketosis to burn off stored fat. That happens anyway when you cut carbs and keep calories reasonable. It just happens a bit quicker when you decide to cut total calories AND keep carbs low enough to promote ketosis.

    Mark Sisson wrote on October 23rd, 2008
  18. I’m trying to transition to a “semi” PB lifestyle since I’m currently doing too much running, which just seems to beat me up. Still, I enjoy running and working out, so I do want to be able to do a decent amount. Here’s the schedule I’ve been following:

    M: 2 miles slow jog to the track, 12×400 w/200m jogs, 2 miles slow jog back.
    T: Weights: 4 sets each for chest, back, shoulders, biceps, triceps, legs (either squats or deadlifts). 45 minutes slow jogging total (2 mile jog to gym and a 4 mile loop home)
    W: 2 miles slow jog to track, 4 miles tempo, 2 mile jog home.
    H: Same as Tues.
    F: 2 mi to track, 12×200 w/200m jogs,
    S: 2-hour slow jog. Basically a flat-land version of your hike
    Sun: Same as Tues.

    So this isn’t THAT far off from what you suggest (running days are ~1 hour; workout days are 1:30 total, including the running) I’ve been doing this for several months, so I should have adapted to the low carbs by now. I have no problems with the weight workouts on the lower carbs. However, my running workouts have really sucked. I just can’t seem to pick up the pace, even if just for the short sprints. My legs feel totally dead, I don’t really get out of breath or nautious(and quickly recover between repeats and after the workout), I don’t sweat much (and immediately cool off after the workout), and I don’t get the “buzz” afterwards. So my “workouts” are really just alternations between slow jogging and slower jogging. Despite this low intensity, my legs still feel sore and stiff.

    Also, I’ve strained my hamstring twice over the past few months, which is probably a completely different issue, but could also be related to glycogen depletion or maybe dehydration (from loss of fluids

    I’d really like to run even less (i.e, replace the slow running after my weight workouts with 10×100 sprints or 2 miles all-out), but can’t seem to get out of a pitter-patter mode, so end up just jogging slow, which doesn’t satisfy me.

    Any advice? Does this sound like glycogen depletion to you? Seems odd that my weight workouts would go great, but my runs would be so bad.

    Thanks!

    ebrunner wrote on November 6th, 2008
  19. I have been following a low carb diet since the onset of my running addiction (lol), about 1.5 years now, but I do mostly run under 60 minutes at a time, and focus more on speed than marathon type endurance. I slow down quite a bit as distance increases, but I don’t know if that’s due to my diet or simply cos I haven’t been running that long yet. I broke 20 minutes in my first 5k, and I’m almost 40, so yes you can perform quite well on low carb.

    I have found that if I take carbs on board before/during/after exercise, I can work out as long and hard as carb-heads. If I don’t, I start feeling dramatically crappier at about 75% MHR. I like to use a mix of 60% maltodextrin/40% sugar, with some whey protein, electrolytes, and glutamine.

    So I use the same fuel strategy that everyone else would use b/d/a runs or bike rides, and otherwise eat low carb. Seems to work, I hasten to add that I would eat more carby stuff if I could, but it makes me sick, so I can’t even if it was a great idea… but low carb meals make me feel so good, and high-carb so bad, that it’s hard for me to believe that I “need” to eat more carbage.

    The one “carbage” I am quite fond of is beer. I love microbrewed beer, single digit bodyfat %age be damned!

    gary d wrote on November 7th, 2008
  20. sorry, forgot to add, for the “ebrunner” question…I run intervals twice a week, 200’s and 400’s, at a fast (for me) pace, about 5.30/mile pace or so. The “key” that will open your muscles to high-speed work is sugar, that is my experience. Take it like I said, before/during/after, I take about 75-125g of sugar total depending on how I feel… then I put it away and go back to low carb. I can’t go fast without the sugar myself, and I’ve been low carb for 4 years! The recipe for my drink is on my blog page.

    gary d wrote on November 7th, 2008
  21. Thanks Gary.

    What do people think about reloading with fruit (especially bananas)? One could still be eating mostly PB-style, just with a higher carb intake.

    About how any carbohydrates are needed to fuel a hard interval workout (i.e., 12×400 w/200m jogs)? That’s ~3 miles hard (I’m assuming 100% carb-fueled); I figure 100 calories/mile, so 300 calories, or 75g beyond what I would eat on a slow day? Or can some of this glycogen replaced by converting lactate back to glycogen, or from gluconeogenisis, etc?

    All told, the workout ends up being 8-9 miles, with warmup, cooldown, recovery jogs; but I’m assuming that because this all low intensity, it’s fueled by fat. Or does all running require at least some additional carbohydrate to recover? I.e, if I go for a one hour easy run, do I use any glycogen?

    It’s odd to me, because I’m not exercising much more than Mark suggests, yet I’m struggling so much with it.

    ebrunner wrote on November 20th, 2008
  22. ebrunner, the hard interval workout in and of itself can be done on just the glycogen stored from the prior 24 hours even on a low-carb program. The issue is whether the interval is done on a day after or among several other days of running medium-to-high pace. Then you can’t be expected to refill glycogen that quickly, That’s why the PB system says do low level (walk, hike, easy ride) stuff that burns mostly fats…then once a week do intervals. That one workout might require 200 grams of glycogen, but it’s all there. Then, as long as you don’t have to run tomorrow, you can take your time refilling glycogen on a low-carb program. If, OTOH, do have to run tomorrow, you’ll need those 200 carbs put back quickly, in which case you reach for the fruit or the potatoes, yams etc. Make sense?

    Mark Sisson wrote on November 20th, 2008
  23. Makes sense, thanks. So, under a low-carb program, total volume of intense training has to be limited, and “easy days” have to be very easy in order to recover.

    Which begs another question: if under a low-carb program, would it be better (for the purposes of fat burning/body composition, not athletic performance ) to do the 12×400 type workout once every three days, or do 4×400 every day? Total volume of intense running is the same in either scenario. My guess is that the daily workout would be more effective because one is creating the post-workout environment every day (GH release, EPOC, etc.), but I wonder if the magnitude of this hormone response is related to volume, so much so that either protocol would have the same effect.

    ebrunner wrote on December 15th, 2008
  24. ebrunner, 4 x 400 every day gets you nothing in terms of adaptation. 12 x 400 once a week might. Even 12 x 400 every three days is too much (if you are doing it right)

    Mark Sisson wrote on December 15th, 2008
  25. Mark, I’m talking purely for fat-burning and hormone response purposes, not for exercise performance. I realize the 4×400 every day is useless for a distance runner looking to improve performance, but what about someone who is simply looking to keep their GH elevated as they age? I

    If 12 x 400s is a once/week workout, what about 6×400 twice a week? Or 10×100 every morning? I get a bit of a buzz from doing some intense running (even a small amount) that fires me up for the rest of the day; I’d rather get this buzz daily vs. doing a longer workout once/week. Is that possible, or does one have to have several very easy days with no intense running at all in order to stockpile glycogen?

    ebrunner wrote on December 15th, 2008
  26. GH requires short intense bursts. If it’s something you can do every day without getting injured after a while, it’s probably not intense enough. Running is just one part of training. You might sprint once (or at most twice) a week. then you might do a heavy leg lift day once a week. Those two or three workouts would be sufficient (and recommended) to maximize HGH output. The rest of your exercising would go toward low level aerobic acitivity, play, or “maintenance” full body work….and, of course, recovery – the most important part of training.

    Mark Sisson wrote on December 15th, 2008
  27. I am on a very Low-carb diet ie Atkins Induction phase <20g carb per day, but have 2 slices of wholegrain multi-seed bread after my 1hr swim in the morning & an apple before my dumbell workout in the evening,
    I am considering a pre-w-o carb up once a week to enable me to perform a very heavy kg workout of compound weight lifting exercises to raise muscle mass in order to burn more fat.
    Will coming out of ketosis slow my fat burning or would it be worth it?
    All comments appriciated

    Kaan

    Kaan wrote on December 28th, 2008
  28. coming out of ketosis does slow your fat-burning somewhat, but if you are already at low body fat, it probably doesn’t matter.

    mark sisson wrote on January 5th, 2009
  29. So what do our muscles use when we are in ketosis for fast energy?

    I’m eating very low carbs (below 20g/day) and doing intense but short interval training w/ weights, kettle bells and body weight 5 days a week. I’m concerned that I’m not getting enough carbs to make my exercise effective, both in terms of gaining lean mass as well as sacrificing my energy overall. Do I need to eat more carbs if I’m exercising in this way?

    Matt wrote on January 8th, 2009
  30. Matt, if you’re exercising less than 40 minutes a day, you won’t use that much glycogen that you can’t replenish it through gluconeogenesis

    Mark Sisson wrote on January 8th, 2009
  31. Mark,

    I am an avid runner and have been for many many years. Recently (about 2 weeks now) I started a ketogenic diet (very very low carb) for weightloss as well as other health benefits. I have continued running, spinning, and swimming with no problems yet that I can tell. In the past before an event (10k, tri, etc) I would take a gu pack about 30 minutes before. I am running a 10k race this weekend and am hoping for about 6:30 pace and was wondering if you think I should take the gu prior to the race or if you think that I should be able to reach that goal even at a very low carb/glucose state? Thank you so much for any advice you can give.

    Armand

    armand wrote on February 12th, 2009
  32. Armand,

    If you have not been training with it, then don’t take it. I myself have adopted a low carb diet while training for endurance athletics with a lot of success. I say as long as you fuel properly the day BEFORE, and morning OF the race, then you will probably be fine. Although, it won’t hurt to bring it with you just in case!

    Best,
    Ryan

    Ryan Denner wrote on February 12th, 2009
  33. Ryan,

    Thanks for the reply. I totally understand and usually stand by the don’t do it if you haven’t trained with it moto. I guess my ignorance is that I have always loaded up on the pasta, bread, and other starches that I am no longer consuming therefore don’t really know what to fuel properly with the day before without having carbohydrates and coming out of ketosis. Any ideas? Thanks so much!!

    Armand

    armand wrote on February 12th, 2009
  34. During the day before, try some potatoes and/or brown rice to top off the glycogen stores (no processed carb like pasta/bread). If you are worried about sugar, then have some low fiber fruit in the morning. Also, before the next time you do a 10K, do a tempo run at 10K pace for say 30 minutes, and see how your body feels. I’d definitely look at this 10K as a learning experience and see how your body deals with racing on low carb. It definitely is doable. Again, take the gel with you just in case.

    Ryan Denner wrote on February 12th, 2009
  35. thanks again Ryan. You have been a big help. I agree with you about looking at this race as learning experience. Hopefully all will go well. I guess with starting a different eating lifestyle I am just a little anxious b/c I know what I am capable of in the past and hope to do as good or better. Thanks again!!

    Armand

    armand wrote on February 12th, 2009
  36. Armand, I agree with Ryan. Take a gu packet with you just in case, but the truth is, a 10k in 37-38 minutes will “only” require about 200 grams of stored glycogen. You should have enough stored if you taper or take the day or two before the race easy

    Mark Sisson wrote on February 12th, 2009
  37. Thanks Mark!! Again I guess my ignorance about low carbohydrate intake and glycogen is becoming more and more evident. I was under the impression that severly reducing carbohydrate intake lead to depletion of glycogen stores requiring your body to get energy solely from fatty acids.

    armand wrote on February 12th, 2009
  38. The body is always getting energy from a combination of fats, glucose/glycogen, protein and carbs. Low carb intake causes you to burn more fat, but also prompts gluconeogensis (because you still need SOME glucose). That is driven by fat metabolism and ketone formation. When you race while trained to burn fats, you still need some glycogen in the muslces. When glycogen is depleted, you hit the wall (you can still walk or jog easily, but can’t run fast). That’s why you might carry the gu….just in case. Probably won’t be a factor in a 10k, but would be more so in a hard, fast triathlon or marathon.

    Mark Sisson wrote on February 12th, 2009
  39. Excellent!!! I really appreciate all the help. I think I understand that aspect better now. One other question I had was, lately if I really push myself on a run (3 – 5.5 miles) I notice a little more cramping in my quads than pre ketogenic diet. Do you believe this is some effect of the diet or just a failure on my part to hydrate correctly or proper electrolyte intake?

    armand wrote on February 12th, 2009
  40. I am not sure if “they” have ever figured out what causes cramping. “They” used to think it was electrolyte imbalance, but the latest theory is your muscles cramp because they are not used to doing a certain motion/load. It might be either, or hydration, or a combination of some/all. Regardless, your muscles cramp b/c they can’t do what you want them to do anymore!

    Try keeping with your diet, *maybe* hydrating a little more, ran at this “hard” pace a little more often (do you warm up properly before running hard?), and maybe even included some stretching, you would stop getting cramps, or at least reduce them. Remember – its all about finding what works for you, so experiment!

    Let us know how it goes!

    Ryan Denner wrote on February 12th, 2009

Leave a Reply

If you'd like to add an avatar to all of your comments click here!

© 2014 Mark's Daily Apple