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In a post about triglycerides, VLDL and carbs, Ned Kock recently commented:

The reality is that very little of the glucose/fructose from carbs gets past the liver in a health person. Muscle glycogen synthase activity is elevated days after an acute glycolitic event (e.g., an intense weight training session).

The liver is a smaller glycogen tank (about 100 g) that fills up quickly, and that is used to replenish the bigger muscle glycogen tank (about 500 g). That happens over time though, and always after the needs of the brain are met.

I need to brush up more on my physiology, but thought I'd do a quick sanity check here. Does this sound right to you? It surprised me. I thought muscle glycogen would be quickly replenished via serum glucose.

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Keeping the liver (and thus brain) stocked up with glucose is a very pressing concern for the body and it therefore has a much higher priority. It's not that hard to saturate the liver's stores though, so muscle glycogen synthesis would simply be second in line. I doubt that both depots would have the same priority. Muscle glycogen is a possible necessity, whereas glucose for the brain is a constant necessity. – Travis Culp♦ Dec 15 2011 at 20:13

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The whole glycogen deal is vastly misunderstood by just about everyone in the paleo community from what I read. They are still stuck on the assumption that fructose has to be processed by the liver before it can be used or that once the liver is full fructose will be turned to fat. Its been shown in overfeeding studies that very little of the carbs become fat unless you overfeed massive amounts for days without physical activity. Its also been shown that sucrose behaves nearly identical to pure glucose(starch) in regards to glycogen muscle storage, it even seems to have some benefits over starch with lower insulin levels and faster uptake according to one study.

I doubt what ted said is true based on my personal observations but I don't really see anything in scholar on the subject. Lots of info on glycogen storage after exercise though.

"The pattern of muscle glycogen resynthesis following exercise-induced depletion is biphasic. Following the cessation of exercise and with adequate carbohydrate consumption, muscle glycogen is rapidly resynthesised to near pre-exercise levels within 24 hours. Muscle glycogen then increases very gradually to above-normal levels over the next few days. " http://ukpmc.ac.uk/abstract/MED/2011684

"When 0.35 (low glucose: N = 5), 0.70 (medium glucose: N = 5), or 1.40 (high glucose: N = 5) g.kg-1 body weight of glucose were given orally at 0, 2, and 4 h after exercise, the rates of glycogen synthesis were (mean +/- SE) 2.1 +/- 0.5, 5.8 +/- 1.0, and 5.7 +/- 0.9 mmol.kg-1.h-1, respectively. When 0.70 g.kg-1 body weight of sucrose (medium sucrose: N = 5), or fructose (medium fructose: N = 7) was ingested accordingly, the rates were 6.2 +/- 0.5 and 3.2 +/- 0.7 mmol.kg-1.h-1" http://ukpmc.ac.uk/abstract/MED/3316904

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 So what happens to the carbs Cliff? If the body can't store them directly and doesn't convert the excess to fat, what happens? And why do we have an obesity epidemic? – AndyM Dec 15 2011 at 23:18
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 So 4000 calories from carbs for multiple days, without any offsetting activity to use glycogen, plus the required nutrition from protein and fat, and you don't gain weight because the carbs magically disappear? Yes, I read that part, and it explains nothing, like your reply. – AndyM Dec 15 2011 at 23:52
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 Don't worry cliff, I have excellent comprehension skills. There must just be something about your lazy dismissive style that leaves these open questions. So you're saying my metabolism will uprate to burn 6000 calories a day without doing any specific physical activity if I eat lots of sugar? That's good news. I imagine I'd get rather hot though. And it's also good to know that there is no link at all between carbohydrate consumption and obesity. The lack of supporting evidence, science or logic isn't likely to put me off, because you're just so persuasive. – AndyM Dec 16 2011 at 0:08
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 ...even using highly refined sources. Its obvious that your cognitive bias wants me to be wrong as is apparent by your blatant misunderstanding of my post. In your mind its obvious that its the carbohydrates that makes SAD dieters fat and not the dietary fat(which is stored in fat tissue the easiest out of any macro-nutrient) which makes up 50% of there diet. – cliff Dec 16 2011 at 0:23
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 Andy: It's highly inefficient to convert glucose into fat (23% energy loss) vs. merely super-saturating glycogen stores which results in a mitochondrial energy substrate switch to glycogen until the stores are brought back to normal levels. DNL, even during carb overfeeding, accounts for about 10g of fat per day. Look at any obese person and probably 95%+ of the actual fat you see started out as dietary fat. Nobody gets obese overfeeding with plain bread or rice. Sure, carbs can cause that aforementioned substrate switch, but the fat was fat to begin with. – Travis Culp♦ Dec 16 2011 at 1:58
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Depends on what you mean by "slowly". My recollection is that research on recovery in athletes was 24-48 hours for glycogen restoration.

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As cliff stated, muscle glycogen stores are replenished at speeds in proportion to the amount of glucose consumed.

There seems to be a lot of misinformation here about CHO intake and fat accumulation. In summary, carbs are converted to fat via a process called de novo lipogenesis. However, de novo lipogenesis occurs in negligible amounts until your entire CHO intake exceeds your total energy expenditure. The body will always prefer CHO to fat/protein for fuel, if available. Here was one study on it: http://www.ncbi.nlm.nih.gov/pubmed/10365981

Unless you're eating something like 700+g CHO a day and are actually exceeding your daily energy expenditure, you get fat not because CHO is converted to fat but rather because lipolysis is downregulated. You aren't burning the fat you eat since you're burning CHO, and it gets stored. VLCDs work for weight loss for a multitude of reasons, but the return to a primarily lipolytic state (vs. lipogenic with high carb + fat intake) is an integral factor.

To answer your actual question, you can check out studies but 24 - 48 hours is sufficient to fully replenish glycogen stores. Ned's statement doesn't jive with what most studies have shown on glycogen replenishment in athletes.

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Would you say there is no link between CHO consumption and fat storage? Or that eating 700g of carbs is particularly difficult or exceptional with SAD? I've no argument with the idea that a healthy person can successfully buffer occasional carb 'overload'. I think it takes concerted effort to get into a problematic fat storing vicious circle. But when limited to the obese population for whom it's relevant, CHO intake can be that high, what gets stored and what gets burned isn't actually all the relevant, and advice to cut fat is not constructive. – AndyM Dec 16 2011 at 2:19
There's definitely a link between CHO consumption and fat storage, but you can't look at it in isolation. Fruitarians eat nothing but fruits and thus up to 90/5/5 carbs/protein/fat but frequently suffer from a failure to thrive after some time. Low body weight, low muscle and bone mass, etc. There's more than just CHO intake when it comes to weight loss. 700g of carbs/day is easy with sugary drinks, yes, though I'd argue that what gets stored and what gets burned is all that's relevant. I don't think I ever stated anything about cutting or not cutting fat. – Silverspeed Dec 16 2011 at 2:34
I'm kinda confused at what you're refuting in the last part of your comment - I never said that eating lots of carbs was good for you or that restricting fat was bad. I simply explained the metabolism behind CHO and fat storage. – Silverspeed Dec 16 2011 at 2:35
Whoops, *restricting fat was good. I don't think fat restriction is beneficial (kinda like everyone on this whole site :). – Silverspeed Dec 16 2011 at 2:36
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 Andy get a clue, your feelings are obviously hurt because we don't agree with your made up dogma. I eat 700g+ of carbs a day, SAD eaters don't even come close to that considering I eat 4000+ cals and my carb percentage is 70%. The SAD is 50/50 fat/carbs(by calories) with the fats being from toxic PUFAs which screw up carbohydrate metabolism(along with tons of other consequences). Most sad eaters are probably getting more like ~300g of carbs and 150g of fat, if they were truly high carb low fat they wouldn't be obese. – cliff Dec 16 2011 at 14:30
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Depends how much glucose you take in. As we know if you take a big hit it''s not going to stay glucose for long. And what I've seen suggests that there's questionable gain to trying to overload things post workout, and only then so as to be able to overtrain. If you have a healthy intense training frequency, then you should be able to refill your glycogen over several days from your normal paleo carb intake/gluconeogenesis if that's your thing.

There's still some CW around I think that suggests that the glucose helps with the uptake of protein, which I hear is not necessary.

So the question is, when you go for your PWO sugar rush, does the insulin preferentially shuttle glucose to the muscles? Fructose has to go to the liver first, so that's a non-issue, but glucose can be used and stored directly. However it seems to me reasonable to think that at best, muscle and liver glycogen are replenished at the same rate, and once the liver is full it's going to start converting to fat while your muscles are only 1/5th full. I think you'd be able to push on and get a lot into the muscles, but only at a cost which may seem counter-productive depending on your goals. Health or performance.

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Hey Andy, I don't think these statements are right. Gluconeogenesis will contribute negligible amounts of glucose to glycogen replenishment - it's primary purpose is to maintain blood glucose levels. It's worth noting that it takes 2-3g of protein to form 1g of glucose. Also, insulin is a highly anabolic hormone and does increase the rate of protein synthesis. See ncbi.nlm.nih.gov/pubmed/16545079 – Silverspeed Dec 16 2011 at 2:14
It'll happen slowly, but it'll happen. HGs didn't go desperately looking for fruit or yams after a hunt. They overconsumed on fat and protein. We adapted to what was available, not necessarily what would be most efficient. With regards protein synthesis, the activation of GLUT-4 after exercise makes additional insulin largely redundant. There's some of course, because you ate protein. – AndyM Dec 16 2011 at 2:24

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