Many of you know I’ve been doing keto for over three years, with a couple of breaks when i had to regain some weight. So it’s always fun to realize that there is still more to learn about how the body processes different types of energy. I’m very active, and have a lot of lean muscle mass, and while I’m not as lean as I was when I was underweight (which is a good thing!) I do have a relatively low body fat percentage (I don’t know exactly because I stopped weighing and measuring myself but I’d guess I’m around 20% or so which is considered “athletic” for women.) My question is, I am trying to understand the process by which my body would “replenish glycogen stores” when i eat some non keto foods, which I do probably once a week. I don’t freak out about having 100 or 150 grams of carbs occasionally because I have no metabolic disorders and I’m so physically active. Since I have a history of restrictive eating disorders, allowing myself to eat some cookies or whatever on occasion helps me stay balanced mentally. But I am curious about how my body utilizes the extra carbs. When I hear discussions about people on keto who have an occasional meal where they consume a higher amount of carbs, it is often said that the excess carbohydrate will just go to replenishing glycogen stores in the muscle and liver. However, it’s my understanding that these glycogen stores are kept sufficiently “full” while on keto due to gluconeogenisis. Most days I eat pretty close to zero carb/carnivore, with a small amount of green vegetables and as much fatty meat as it takes to feel satiated . I fast for around 20 hours a day and always do fasted workouts in the mornings. So what is happening when I exercise in the morning, fast until around dinner, and then consume “excess” carbohydrates? Are my glycogen stores “replenished “ from gluconeogenisis already and the carbs end up floating around in my blood stream and pounding their inflammatory signals into my arterial walls?? (That is a joke, haha)…or do they truly replenish glycogen stores, which would mean that most of the time I’m walking around with depleted muscle and liver glycogen?
“Replenishing glycogen stores”
Bookmarked. I’m thinking of bumping up to this as I’ve leaned way the heck out, and yesterday’s 2-on-1 sparring session drained me within a minute.
I thought Phinney et al discovered that at most glycogen in a fat adapted person repletes to 60% of a carb burner’s level. The liver will take the glycerol from triglycerides during fatty acid oxidation and can make glucose, but I’m also a little unclear as to when that fresh glucose molecule will get added to glycogen. Especially if we’re fasting all the time and eating little to no carb.
Maybe when the liver senses the serum glucose level is fine, and can manage it there easily, then it’ll take what carbs are provided whether from food or FA oxidation and start to store them away for a rainy day (liver glycogen).
I’m interested in muscle glycogen and keeping that high(er) without going overboard. And I’m not a fan of yams…
I think this approach is very contentious and for some the occasional foray outside of keto is a great long term strategy especially if you’re lean and active. But it does make curious about that glycogen storage situation. I know gluconeogenisis is demand driven, but what happens when you’re keto and you do a hard workout and you fast afterwards? Is fat being burned or is glycogen being produced? And that begs th question of what happens if you have a higher carb intake on occasion? I can kind of feel the “hangover” effect of it mentally the next day, which usually clears up after a good workout. I can definitely tell when I’m deep in ketosis vs when I eat too many carbs. I guess to further that question, if you eat a higher amount of carbs one night, workout fasted the next morning and clear out the extra glucose, what substrate does your body start to utilize after that if you keep fasting?
If we had an easy way of measuring glycogen it would be a perfect world. Since no one can tell you what your level is, and you can’t know from one moment to the next… (hmm I wonder if that 2-deoxyglucose they use for cancer treatment or the other funny glucose they use for detection in the PET scans could be used somehow) … what your levels actually are, it’s just something to manage.
Atkins and Westman’s position were/are to increase carbs after the induction period to the point where you know your personal threshold of ketosis. 20g will get most people to ketosis but I think if you’re not metabolically deranged you can handle much more and maintain ketosis.
There’s tricks to keep the dietary sugars from having an impact, eat the carb in the evening, drink ACV/green tea right before, eat the carb at the end of a meal after eating the fat and fiber…
Great question. I’m looking forward to this discussion.
Plus, I would appreciate any insights into ‘set weighs’ and how this could be involved.
@ianrobo to the white courtesy phone.
If you’re fat adapted, the carby dinner will first go to glycogen repletion. I doubt you’re taking in pounds of sugar though so I doubt you’ll fully replete from one dinner. (Once glycogen is fully repleted, whatever that level is for you, after that you’ll get DNL, right?)
So the morning workout, if you can keep your heart rate low, you’ll use fatty acid oxidation for the ATP. If you’re heart rate goes higher (according to MAF) into the glycolytic zones, you’ll burn the muscle glycogen up, so try to keep heart rate in the proper zones for best results.
Ok interesting question so let me say I have tried it once with Fish and chips then a fasted event - about 120Km and felt no difference and before Flanders I had a few cheeky beers with no impact.
Now these were at higher levels of Zones - tempo mainly which is above MAF of course … the point being one night may replenish stores but if you ride next day and fully fat adapted as FASTER showed you do not use those anyway until much higher levels of power than a carb burner …
Thanks Ian!
So are the muscle glycogen stores ‘locked in’ and only used by the muscle?
I usually do OMAD and am under the impression that liver glycogen is used to maintain serum glucose under a ketogenic regimen and is usually nearly tapped out after around 24 hours fasted…
That’s too scientific for me to answer 
but atvtgevfibushnof Flanders I felt great and no muscle soreness or tiredness apparent … so good next day did another 60km.
So since going Keto then fat adapted not once dis I feel as bad as I ever did as a carb burner and recovery to me is far more the key then any on the day feeling
There’s the concept of energy substrate competition, in that, which of the macros you eat, including alcohol and now exogenous ketones (but put them aside for a moment) are burned. The priority is going to be which macro do you have the ability to store the most?
You can’t store alcohol period, no matter how hollow your leg is said to be, so this is why ketosis is ‘paused’ when even fat adapted people drink. Once the ethanols are metabolized, FFAs go back to B-oxidation.
The next macro you have the least ability to store is carbs. Fructose the very least, it goes down its pathway, depending on your biochem understanding, Lustig or Feinman, back around to a triglyceride to be shuttled to an adipocyte or ectopically depending on your level of IR . Glucose hangs around to be used depending on insulin levels. Now a long time fat adapted person may’ve developed a down-regulation of insulin receptors (beneficially) in the muscle cells to spare glucose not for muscle use but for RBCs and specific neurons (and I forget what other cells) and that is what is called the peripheral insulin resistance. And may be the cause of the around 60% value of glycogen repletion in fat adapted athletes.
I assume any glucose above the normal serum levels the liver maintains will try to be added to liver and muscle glycogen.
Protein. Can’t store protein. As @richard will tell you, it’ll get deaminated if there’s no demand and excreted. Demand is a funny term and I’m not sure how to tell you when the best time to eat protein is other than after a workout. Luckily workouts bump insulin a bit and that bump can conceivably help to shuttle sugar and protein to muscle given good sleep and time to recover.
Then fats. I will always appreciate how long the energy tends to stick around after a good MCT/coconut oil coffee.
@Dipper_Actual this is exactly the response i was looking for. Brilliant!
I don’t think gluconeogenesis while being lipolytic is sufficient for maintenance of stored glycogen. Following a 35% protein macro certainly won’t do it. Besides, glycogenolysis occurs while secreting glucagon rather than insulin.
It really takes quite a few carbs to recompensate glycogen, one meal won’t do it. Most, if not all the carbs for one meal probably won’t even make it out of the digestive system, and will be preferentially burned rather than converted to glycogen. During a 36hr recompensation, I usually test positive for ketones during the first 24hrs, so recompensation can be a fairly long process.
IMO, Atkins second and third phase concepts were flawed, as it was all about finding your Carb intake maintenance level. Too much possibility of Carb levels creeping upwards to the point lipogenic readaptation begins. A better strategy is intermittant Carb intake, allowing glycogen levels to drop between intakes so there’s no possibility of chronic overcompensation. That’s what works for me.
Oh that is fascinating!! I was really excited to hear some good scientific explanations of energy substrate useage. I’m finishing up my personal training certification and I like understand how the body’s energy systems respond to different physical activities.
Fascinating, thanks @240lbfatloss !! That makes the 20-40g of white rice from a tuna/avocado roll not so angsty hah!
Another subject I should address is the difference in Carb intakes for fat loss and Maintenance. For fat loss, glycogen levels need to be completely depleted for efficient fat loss. So, unless you’re very active or training, your Carb intake should be lower, such as one meal eaten occasionally, so your glycogen completely depletes and lipolysis in optimized. A simple strategy for those adapted and still trying to lose fat is to eat some carbs on one or two days on the weekend, allowing optimal lipolysis during the rest of the week.
For Maintenance, Carb intake can be more frequent, as the intent shifts from glycogen depletion to prevention of glycogen overcompensation. So, depending on the individual, you could eat carbs as often as every other day, without intentionally overeating, allowing glycogen levels drop on your non Carb days. You’d see a minor weight gain as you’d probably be maintaining some level of stored glycogen, but it would probably be minor. You could easily see how much if you extend your non Carb days a few more (while limiting salt) to totally deplete and get an accurate scale reading. You should be able to confirm no weight gain at that time. You may even be able to confirm additional fat loss if you experience positive metabolic effects due to the limited Carb intake.
Usually, if I’m eating carbs with a meal, I’ll limit my fat intake to avoid the synergistically increased insulin spike of a carb-fat combination. But not always. If I’m having a nice steak or roast beef I’ll still have my baked potato with sour cream, chives and bacon. Or my roast potatoes with garlic, rosemary and olive oil.
@Dipper_Actual I was curious about your comment that we can’t utilize protein as an energy substrate. I knew that we can’t use it directly but I’d thought “excess” protein was converted to fat, but you say it gets deanimated and excreted. Is there a study that shows how that process works?
Came across this video from a few weeks ago that answered a couple questions in my head. Mainly about rep ranges with non-refeeding keto diet.
I’ll jump in quickly. Complete protein can be used as the substrate for gluconeogenesis. But, it’s not a very efficient process and can no way meet bodily glucose requirements like carbs can. That’s why we get sick on high protein diets. Really it provides limited glucose for the brain.
No, protein certainly can be burned for energy if needed. Just saying that the order will be after glucose and before fat since we don’t have a really good way to store it.