Anyone found any good research articles on glycogen replenishment within a low carb diet? I’m asking because I’ve maintained a fairly intense lifting workout schedule on an Atkins induction-style WOE and I can’t explain why I don’t fatigue more easily if I’m truly "depleted" of glycogen. I want to know more.
Some thoughts: when we deplete glycogen initially on a low carb diet to initiate ketosis, we still replenish that glycogen, correct? The glycogen then would have to come from (I assume) the breakdown of ketone bodies, protein, or tiny amounts of carb in an induction diet being converted into blood glucose. Does glycogen not replenish as quickly from ketone sources as it does from carbohydrate sources?
Most studies look at glycogen replenishment from the standpoint of someone NOT initially in ketosis, but from someone who may have just finished strenuous exercise. Does it work differently if the subject is in ketosis?
My under-informed hypothesis would go something like this: The body seeks to fill its glycogen reserves on a constant basis, particularly in response to feeding. If feeding stimulates little insulin because of a VLC diet, the body is still regularly converting ketones to blood glucose, and a portion of that is being squirreled away as glycogen all the time. Thus, the body is constantly "sopping up" some of its available blood glucose to replenish glycogen (perhaps even on a more regular and constant basis than in an carb-induced insulin spike) and as a result, as blood glucose is removed from the system, the body draws on lipolysis to create more ketones and thus more blood glucose – since it finds no available substrate in the form of carbohydrate, and finds plenty of excess ketone bodies floating around). This would have the advantage of keeping one in a lipolytic/fat-burning state while maintaining stable blood glucose and sparing protein.
I’m just wondering if anyone’s seen the research to explain the process or point out observations about it that specifically addresses individuals on a VLC diet. Since our bodies can only hold something around 2000 calories in glycogen, if I deplete 1000 of those in an hour workout, how long do they take to replenish vs. a high-carb diet with more definite insulin spikes?
Most of what I’ve read (again, not dealing with VLC diets) says glycogen depletion takes more than 24 hrs to recover from, and that a lot of factors affect recovery (age, gender, smoking, carb intake, etc.) But if I burn up, say 1000 calories in glycogen daily, and on a VLC diet I’m not replacing them just as rapidly, after a few days I should feel unable to maintain my workouts at the same intensity – but I’m finding (anecdotally) that isn’t true, and I know I’m not taking in 1000 calories’ worth of carbohydrate or even protein that could be converted into that glycogen replenishment. Do our bodies, while in a ketotic/lipolytic state, "convert" to fuel our glycogen stores by using dietary fat, body fat, or both? If so, how rapidly or slowly does this occur?